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UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

Commission file number: 0-7275

CULLEN/FROST BANKERS, INC.

(Exact name of registrant as specified in its charter)

(210) 220-4011

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

      Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.     Yes þ          No o

      Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.     Yes o          No þ

      Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.     Yes þ          No o

      Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.     o

      Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Act.)     Yes þ          No o

      Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act.)     Yes o          No þ

      As of June 30, 2005, the last business day of the registrant’s most recently completed second fiscal quarter, the aggregate market value of the shares of common stock held by non-affiliates, based upon the closing price per share of the registrant’s common stock as reported on The New York Stock Exchange, Inc., was approximately $2.4 billion.

      As of January 27, 2006, there were 54,553,185 shares of the registrant’s common stock, $.01 par value, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

      Portions of the Proxy Statement for the 2006 Annual Meeting of Shareholders of Cullen/Frost Bankers, Inc. to be held on April 27, 2006 are incorporated by reference in this Form 10-K in response to Part III, Items 10, 11, 12, 13 and 14.

CULLEN/FROST BANKERS, INC.

ANNUAL REPORT ON FORM 10-K

TABLE OF CONTENTS

PART I

      The disclosures set forth in this item are qualified by Item 1A. Risk Factors and the section captioned “Forward-Looking Statements and Factors that Could Affect Future Results” in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations of this report and other cautionary statements set forth elsewhere in this report.

The Corporation

       Cullen/Frost Bankers, Inc. (“Cullen/Frost”), a Texas business corporation incorporated in 1977, is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its subsidiaries (collectively referred to as the “Corporation”), a broad array of products and services throughout 12 Texas markets. The Corporation offers commercial and consumer banking services, as well as trust and investment management, investment banking, insurance brokerage, leasing, asset-based lending, treasury management and item processing services. At December 31, 2005, Cullen/Frost had consolidated total assets of $11.7 billion and was one of the largest independent bank holding companies headquartered in the State of Texas.

      The Corporation’s philosophy is to grow and prosper, building long-term relationships based on top quality service, high ethical standards, and safe, sound assets. The Corporation operates as a locally oriented, community-based financial services organization, augmented by experienced, centralized support in select critical areas. The Corporation’s local market orientation is reflected in its financial centers and regional advisory boards, which are comprised of local business persons, professionals and other community representatives, that assist the Corporation’s financial centers in responding to local banking needs. Despite this local market, community-based focus, the Corporation offers many of the products available at much larger money-center financial institutions.

      The Corporation serves a wide variety of industries including, among others, energy, manufacturing, services, construction retail, telecommunications, healthcare, military and transportation. The Corporation’s customer base is similarly diverse. The Corporation is not dependent upon any single industry or customer.

      The Corporation’s operating objectives include expansion, diversification within its markets, growth of its fee-based income, and growth internally and through acquisitions of financial institutions, branches and financial services businesses. The Corporation seeks merger or acquisition partners that are culturally similar and have experienced management and possess either significant market presence or have potential for improved profitability through financial management, economies of scale and expanded services. The Corporation regularly evaluates merger and acquisition opportunities and conducts due diligence activities related to possible transactions with other financial institutions and financial services companies. As a result, merger or acquisition discussions and, in some cases, negotiations may take place and future mergers or acquisitions involving cash, debt or equity securities may occur. Acquisitions typically involve the payment of a premium over book and market values, and, therefore, some dilution of the Corporation’s tangible book value and net income per common share may occur in connection with any future transaction. During 2005, the Corporation acquired Horizon Capital Bank (Houston market area) and announced definitive agreements to acquire Texas Community Bancshares, Inc. (Dallas market area) and Alamo Corporation of Texas (Rio Grande Valley market area). Details of these transactions are presented in Note 2 — Mergers and Acquisitions in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which is located elsewhere in this report.

      Although Cullen/Frost is a corporate entity, legally separate and distinct from its affiliates, bank holding companies such as Cullen/Frost are generally required to act as a source of financial strength for their subsidiary banks. The principal source of Cullen/Frost’s income is dividends from its subsidiaries. There are certain regulatory restrictions on the extent to which these subsidiaries can pay dividends or otherwise supply

funds to Cullen/Frost. See the section captioned “Supervision and Regulation” for further discussion of these matters.

      Cullen/Frost’s executive offices are located at 100 W. Houston Street, San Antonio, Texas 78205, and its telephone number is (210) 220-4011.

Subsidiaries of Cullen/Frost

      Incorporated under the laws of Delaware, The New Galveston Company is a wholly owned second-tier financial holding company and bank holding company, which directly owns all of Cullen/Frost’s banking and non-banking subsidiaries with the exception of Cullen/Frost Capital Trust I and Cullen/Frost Capital Trust II.

      Cullen/Frost Capital Trust I (“Trust I”) and Cullen/Frost Capital Trust II (“Trust II”) are Delaware statutory business trusts formed in 1997 and 2004, respectively, for the purpose of issuing $100 million and $120 million, respectively, in trust preferred securities and lending the proceeds to Cullen/Frost. Cullen/Frost guarantees, on a limited basis, payments of distributions on the trust preferred securities and payments on redemption of the trust preferred securities.

      Trust I and Trust II are variable interest entities (VIEs) for which the Corporation is not the primary beneficiary, as defined in Financial Accounting Standards Board Interpretation (“FIN”) No. 46 “Consolidation of Variable Interest Entities, an Interpretation of Accounting Research Bulletin No. 51 (Revised December 2003).” In accordance with FIN 46R, which was implemented in the fourth quarter of 2003, the accounts of Trust I and Trust II are not included in the Corporation’s consolidated financial statements. Prior to the fourth quarter of 2003, the financial statements of Trust I were included in the consolidated financial statements of the Corporation because Cullen/Frost owns all of the outstanding common equity securities of the Trust. See the Corporation’s accounting policy related to consolidation in Note 1 — Summary of Significant Accounting Policies in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which is located elsewhere in this report.

      Despite the fact that the accounts of Trust I and Trust II are not included in the Corporation’s consolidated financial statements, the $220 million in trust preferred securities issued by these subsidiary trusts are included in the Tier 1 capital of Cullen/Frost for regulatory capital purposes as allowed by the Federal Reserve Board. In February 2005, the Federal Reserve Board issued a final rule that allows the continued inclusion of trust preferred securities in the Tier 1 capital of bank holding companies. The Board’s final rule limits the aggregate amount of restricted core capital elements (which includes trust preferred securities, among other things) that may be included in the Tier 1 capital of most bank holding companies to 25% of all core capital elements, including restricted core capital elements, net of goodwill less any associated deferred tax liability. Large, internationally active bank holding companies (as defined) are subject to a 15% limitation. Amounts of restricted core capital elements in excess of these limits generally may be included in Tier 2 capital. The final rule provides a five-year transition period, ending March 31, 2009, for application of the quantitative limits. The Corporation does not expect that the quantitative limits will preclude it from including the $220 million in trust preferred securities in Tier 1 capital. However, the trust preferred securities could be redeemed without penalty if they were no longer permitted to be included in Tier 1 capital. See Note 9 — Borrowed Funds and Note 12 — Regulatory Matters in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which is located elsewhere in this report.

      The Frost National Bank (“Frost Bank”) is primarily engaged in the business of commercial and consumer banking through 83 financial centers and 126 ATMs across Texas. Frost Bank serves the Texas

metropolitan areas of Austin, Boerne, Corpus Christi, Dallas, Fort Worth, Galveston, Harlingen, Houston, McAllen, New Braunfels, San Antonio and San Marcos. Frost Bank was chartered as a national banking association in 1899, but its origin can be traced to a mercantile partnership organized in 1868. At December 31, 2005, Frost Bank had consolidated total assets of $11.7 billion and total deposits of $9.3 billion and was one of the largest commercial banks headquartered in the State of Texas.

      Significant services offered by Frost Bank include:

      Frost Insurance Agency, Inc. is a wholly owned subsidiary of Frost Bank that provides insurance brokerage services to individuals and businesses covering corporate and personal property and casualty insurance products, as well as group health and life insurance products.

      Frost Brokerage Services, Inc. (“FBS”) is a wholly owned subsidiary of Frost Bank that provides brokerage services and performs other transactions or operations related to the sale and purchase of securities of all types. FBS is registered as a fully disclosed introducing broker-dealer under the Securities Exchange Act of 1934 and, as such, does not hold any customer accounts.

      Frost Premium Finance Corporation is a wholly owned subsidiary of Frost Bank that makes loans to qualified borrowers for the purpose of financing their purchase of property and casualty insurance.

      Frost Securities, Inc. is a wholly owned subsidiary that provides advisory and private equity services to middle market companies in Texas.

      Main Plaza Corporation is a wholly owned non-banking subsidiary that occasionally makes loans to qualified borrowers. Loans are funded with current cash or borrowings against internal credit lines.

      Daltex General Agency, Inc. is a wholly owned non-banking subsidiary that operates as a managing general insurance agency providing insurance on certain auto loans financed by Frost Bank.

      Cullen/Frost has various other subsidiaries that are not significant to the consolidated entity.

Operating Segments

       Cullen/Frost’s operations are managed along two reportable operating segments consisting of Banking and the Financial Management Group. See the sections captioned “Results of Segment Operations” in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and Note 19 — Operating Segments in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which are located elsewhere in this report.

Competition

       There is significant competition among commercial banks in the Corporation’s market areas. As a result of the deregulation of the financial services industry (see the discussion of the Gramm-Leach-Bliley Financial Modernization Act of 1999 in the section of this item captioned “Supervision and Regulation”), the Corporation also competes with other providers of financial services, such as savings and loan associations, credit unions, consumer finance companies, securities firms, insurance companies, insurance agencies, commercial finance and leasing companies, full service brokerage firms and discount brokerage firms. Some of the Corporation’s competitors have greater resources and, as such, may have higher lending limits and may offer other services that are not provided by the Corporation. The Corporation generally competes on the basis of customer service and responsiveness to customer needs, available loan and deposit products, the rates of interest charged on loans, the rates of interest paid for funds, and the availability and pricing of trust, brokerage and insurance services.

Supervision and Regulation

       Cullen/Frost, Frost Bank and many of its non-banking subsidiaries are subject to extensive regulation under federal and state laws. The regulatory framework is intended primarily for the protection of depositors, federal deposit insurance funds and the banking system as a whole and not for the protection of security holders.

      Set forth below is a description of the significant elements of the laws and regulations applicable to Cullen/Frost and its subsidiaries. The description is qualified in its entirety by reference to the full text of the statutes, regulations and policies that are described. Also, such statutes, regulations and policies are continually under review by Congress and state legislatures and federal and state regulatory agencies. A change in statutes, regulations or regulatory policies applicable to Cullen/Frost and its subsidiaries could have a material effect on the business of the Corporation.

      Cullen/Frost is a legal entity separate and distinct from Frost Bank and its other subsidiaries. As a financial holding company and a bank holding company, Cullen/Frost is regulated under the Bank Holding Company Act of 1956, as amended (“BHC Act”), and is subject to inspection, examination and supervision by the Board of Governors of the Federal Reserve System (“Federal Reserve Board”). Cullen/Frost is also under the jurisdiction of the SEC and is subject to the disclosure and regulatory requirements of the Securities Act of 1933, as amended, and the Securities Exchange Act of 1934, as amended, as administered by the SEC. Cullen/Frost is listed on the New York Stock Exchange (NYSE) under the trading symbol “CFR,” and is subject to the rules of the NYSE for listed companies.

      Frost Bank is organized as a national banking association under the National Bank Act. It is subject to regulation and examination by the Office of the Comptroller of the Currency (“OCC”) and the Federal Deposit Insurance Corporation (“FDIC”).

      Many of the Corporation’s non-bank subsidiaries also are subject to regulation by the Federal Reserve Board and other federal and state agencies. Frost Securities, Inc. and Frost Brokerage Services, Inc. are regulated by the SEC, the National Association of Securities Dealers, Inc. (“NASD”) and state securities regulators. The Corporation’s insurance subsidiaries are subject to regulation by applicable state insurance regulatory agencies. Other non-bank subsidiaries are subject to both federal and state laws and regulations.

      In general, the BHC Act limits the business of bank holding companies to banking, managing or controlling banks and other activities that the Federal Reserve Board has determined to be so closely related to banking as to be a proper incident thereto. As a result of the Gramm-Leach-Bliley Financial Modernization Act of 1999 (“GLB Act”), which amended the BHC Act, bank holding companies that are financial holding companies may engage in any activity, or acquire and retain the shares of a company engaged in any activity that is either (i) financial in nature or incidental to such financial activity (as determined by the Federal Reserve Board in consultation with the OCC) or (ii) complementary to a financial activity and that does not pose a substantial risk to the safety and soundness of depository institutions or the financial system generally (as solely determined by the Federal Reserve Board). Activities that are financial in nature include securities underwriting and dealing, insurance underwriting and making merchant banking investments.

      If a bank holding company seeks to engage in the broader range of activities that are permitted under the BHC Act for financial holding companies, (i) all of its depository institution subsidiaries must be “well capitalized” and “well managed” and (ii) it must file a declaration with the Federal Reserve Board that it elects to be a “financial holding company.” A depository institution subsidiary is considered to be “well capitalized” if it satisfies the requirements for this status discussed in the section captioned “Capital Adequacy and Prompt Corrective Action,” included elsewhere in this item. A depository institution subsidiary is considered “well managed” if it received a composite rating and management rating of at least “satisfactory” in its most recent examination. Cullen/Frost’s declaration to become a financial holding company was declared effective by the Federal Reserve Board on March 11, 2000.

      In order for a financial holding company to commence any new activity permitted by the BHC Act, or to acquire a company engaged in any new activity permitted by the BHC Act, each insured depository institution subsidiary of the financial holding company must have received a rating of at least “satisfactory” in its most recent examination under the Community Reinvestment Act. See the section captioned “Community Reinvestment Act” included elsewhere in this item.

      The BHC Act generally limits acquisitions by bank holding companies that are not qualified as financial holding companies to commercial banks and companies engaged in activities that the Federal Reserve Board has determined to be so closely related to banking as to be a proper incident thereto. Financial holding companies like Cullen/Frost are also permitted to acquire companies engaged in activities that are financial in nature and in activities that are incidental and complementary to financial activities without prior Federal Reserve Board approval.

      The BHC Act, the Federal Bank Merger Act, the Texas Banking Code and other federal and state statutes regulate acquisitions of commercial banks. The BHC Act requires the prior approval of the Federal Reserve Board for the direct or indirect acquisition of more than 5.0% of the voting shares of a commercial bank or its parent holding company. Under the Federal Bank Merger Act, the prior approval of the OCC is required for a national bank to merge with another bank or purchase the assets or assume the deposits of another bank. In reviewing applications seeking approval of merger and acquisition transactions, the bank regulatory authorities will consider, among other things, the competitive effect and public benefits of the transactions, the capital position of the combined organization, the applicant’s performance record under the Community Reinvestment Act (see the section captioned “Community Reinvestment Act” included elsewhere in this item) and fair housing laws and the effectiveness of the subject organizations in combating money laundering activities.

      The principal source of Cullen/Frost’s cash revenues is dividends from Frost Bank. The prior approval of the OCC is required if the total of all dividends declared by a national bank in any calendar year would exceed the sum of the bank’s net profits for that year and its retained net profits for the preceding two calendar years, less any required transfers to surplus. Federal law also prohibits national banks from paying dividends that would be greater than the bank’s undivided profits after deducting statutory bad debt in excess of the bank’s allowance for loan losses. Under the foregoing dividend restrictions, and without adversely affecting its “well capitalized” status, Frost Bank could pay aggregate dividends of approximately $137.4 million to Cullen/Frost, without obtaining affirmative governmental approvals, at December 31, 2005. This amount is not necessarily indicative of amounts that may be paid or available to be paid in future periods.

      In addition, Cullen/Frost and Frost Bank are subject to other regulatory policies and requirements relating to the payment of dividends, including requirements to maintain adequate capital above regulatory minimums. The appropriate federal regulatory authority is authorized to determine under certain circumstances relating to the financial condition of a bank holding company or a bank that the payment of dividends would be an unsafe or unsound practice and to prohibit payment thereof. The appropriate federal regulatory authorities have indicated that paying dividends that deplete a bank’s capital base to an inadequate level would be an unsafe and unsound banking practice and that banking organizations should generally pay dividends only out of current operating earnings.

      There are various restrictions on the ability of Cullen/Frost and its non-bank subsidiaries to borrow from, and engage in certain other transactions with, Frost Bank. In general, these restrictions require that any extensions of credit must be secured by designated amounts of specified collateral and are limited, as to any one of Cullen/Frost or its non-bank subsidiaries, to 10% of Frost Bank’s capital stock and surplus, and, as to Cullen/Frost and all such non-bank subsidiaries in the aggregate, to 20% of Frost Bank’s capital stock and surplus.

      Federal law also provides that extensions of credit and other transactions between Frost Bank and Cullen/Frost or one of its non-bank subsidiaries must be on terms and conditions, including credit standards, that are substantially the same or at least as favorable to Frost Bank as those prevailing at the time for comparable transactions involving other non-affiliated companies or, in the absence of comparable transactions, on terms and conditions, including credit standards, that in good faith would be offered to, or would apply to, non-affiliated companies.

      Federal Reserve Board policy requires bank holding companies to act as a source of financial and managerial strength to their subsidiary banks. Under this policy, Cullen/Frost is expected to commit resources to support Frost Bank, including at times when Cullen/Frost may not be in a financial position to provide it. Any capital loans by a bank holding company to any of its subsidiary banks are subordinate in right of payment

to deposits and to certain other indebtedness of such subsidiary banks. The BHC Act provides that, in the event of a bank holding company’s bankruptcy, any commitment by the bank holding company to a federal bank regulatory agency to maintain the capital of a subsidiary bank will be assumed by the bankruptcy trustee and entitled to priority of payment.

      In addition, under the National Bank Act, if the capital stock of Frost Bank is impaired by losses or otherwise, the OCC is authorized to require payment of the deficiency by assessment upon Cullen/Frost. If the assessment is not paid within three months, the OCC could order a sale of the Frost Bank stock held by Cullen/Frost to make good the deficiency.

      Banks and bank holding companies are subject to various regulatory capital requirements administered by state and federal banking agencies. Capital adequacy guidelines and, additionally for banks, prompt corrective action regulations, involve quantitative measures of assets, liabilities, and certain off-balance-sheet items calculated under regulatory accounting practices. Capital amounts and classifications are also subject to qualitative judgments by regulators about components, risk weighting and other factors.

      The Federal Reserve Board, the OCC and the FDIC have substantially similar risk-based capital ratio and leverage ratio guidelines for banking organizations. The guidelines are intended to ensure that banking organizations have adequate capital given the risk levels of assets and off-balance sheet financial instruments. Under the guidelines, banking organizations are required to maintain minimum ratios for Tier 1 capital and total capital to risk-weighted assets (including certain off-balance sheet items, such as letters of credit). For purposes of calculating the ratios, a banking organization’s assets and some of its specified off-balance sheet commitments and obligations are assigned to various risk categories. A depository institution’s or holding company’s capital, in turn, is classified in one of three tiers, depending on type:

      Cullen/Frost, like other bank holding companies, currently is required to maintain Tier 1 capital and “total capital” (the sum of Tier 1, Tier 2 and Tier 3 capital) equal to at least 4.0% and 8.0%, respectively, of its total risk-weighted assets (including various off-balance-sheet items, such as standby letters of credit). Frost Bank, like other depository institutions, is required to maintain similar capital levels under capital adequacy guidelines. For a depository institution to be considered “well capitalized” under the regulatory framework for prompt corrective action, its Tier 1 and total capital ratios must be at least 6.0% and 10.0% on a risk-adjusted basis, respectively.

      Bank holding companies and banks subject to the market risk capital guidelines are required to incorporate market and interest rate risk components into their risk-based capital standards. Under the market risk capital guidelines, capital is allocated to support the amount of market risk related to a financial institution’s ongoing trading activities.

      Bank holding companies and banks are also required to comply with minimum leverage ratio requirements. The leverage ratio is the ratio of a banking organization’s Tier 1 capital to its total adjusted quarterly average assets (as defined for regulatory purposes). The requirements necessitate a minimum leverage ratio of 3.0% for financial holding companies and national banks that either have the highest supervisory rating or have implemented the appropriate federal regulatory authority’s risk-adjusted measure for market risk. All other financial holding companies and national banks are required to maintain a minimum leverage ratio of 4.0%,

unless a different minimum is specified by an appropriate regulatory authority. For a depository institution to be considered “well capitalized” under the regulatory framework for prompt corrective action, its leverage ratio must be at least 5.0%. The Federal Reserve Board has not advised Cullen/Frost, and the OCC has not advised Frost Bank, of any specific minimum leverage ratio applicable to it.

      The Federal Deposit Insurance Act, as amended (“FDIA”), requires among other things, the federal banking agencies to take “prompt corrective action” in respect of depository institutions that do not meet minimum capital requirements. The FDIA sets forth the following five capital tiers: “well capitalized,” “adequately capitalized,” “undercapitalized,” “significantly undercapitalized” and “critically undercapitalized.” A depository institution’s capital tier will depend upon how its capital levels compare with various relevant capital measures and certain other factors, as established by regulation. The relevant capital measures are the total capital ratio, the Tier 1 capital ratio and the leverage ratio.

      Under the regulations adopted by the federal regulatory authorities, a bank will be: (i) “well capitalized” if the institution has a total risk-based capital ratio of 10.0% or greater, a Tier 1 risk-based capital ratio of 6.0% or greater, and a leverage ratio of 5.0% or greater, and is not subject to any order or written directive by any such regulatory authority to meet and maintain a specific capital level for any capital measure; (ii) “adequately capitalized” if the institution has a total risk-based capital ratio of 8.0% or greater, a Tier 1 risk-based capital ratio of 4.0% or greater, and a leverage ratio of 4.0% or greater (3.0% in certain circumstances ) and is not “well capitalized”; (iii) “undercapitalized” if the institution has a total risk-based capital ratio that is less than 8.0%, a Tier 1 risk-based capital ratio of less than 4.0% or a leverage ratio of less than 4.0% (3.0% in certain circumstances); (iv) “significantly undercapitalized” if the institution has a total risk-based capital ratio of less than 6.0%, a Tier 1 risk-based capital ratio of less than 3.0% or a leverage ratio of less than 3.0%; and (v) “critically undercapitalized” if the institution’s tangible equity is equal to or less than 2.0% of average quarterly tangible assets. An institution may be downgraded to, or deemed to be in, a capital category that is lower than indicated by its capital ratios if it is determined to be in an unsafe or unsound condition or if it receives an unsatisfactory examination rating with respect to certain matters. Cullen/Frost believes that, as of December 31, 2005, its bank subsidiary, Frost Bank, was “well capitalized,” based on the ratios and guidelines described above. A bank’s capital category is determined solely for the purpose of applying prompt corrective action regulations, and the capital category may not constitute an accurate representation of the bank’s overall financial condition or prospects for other purposes.

      The FDIA generally prohibits a depository institution from making any capital distributions (including payment of a dividend) or paying any management fee to its parent holding company if the depository institution would thereafter be undercapitalized. Undercapitalized institutions are subject to growth limitations and are required to submit a capital restoration plan. The agencies may not accept such a plan without determining, among other things, that the plan is based on realistic assumptions and is likely to succeed in restoring the depository institution’s capital. In addition, for a capital restoration plan to be acceptable, the depository institution’s parent holding company must guarantee that the institution will comply with such capital restoration plan. The aggregate liability of the parent holding company is limited to the lesser of (i) an amount equal to 5.0% of the depository institution’s total assets at the time it became undercapitalized and (ii) the amount which is necessary (or would have been necessary) to bring the institution into compliance with all capital standards applicable with respect to such institution as of the time it fails to comply with the plan. If a depository institution fails to submit an acceptable plan, it is treated as if it is “significantly undercapitalized.”

      “Significantly undercapitalized” depository institutions may be subject to a number of requirements and restrictions, including orders to sell sufficient voting stock to become “adequately capitalized,” requirements to reduce total assets, and cessation of receipt of deposits from correspondent banks. “Critically undercapitalized” institutions are subject to the appointment of a receiver or conservator.

      For information regarding the capital ratios and leverage ratio of Cullen/Frost and Frost Bank see the discussion under the section captioned “Capital and Liquidity” included in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and Note 12 — Regulatory Matters in the

notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, elsewhere in this report.

      The federal regulatory authorities’ risk-based capital guidelines are based upon the 1988 capital accord of the Basel Committee on Banking Supervision (the “BIS”). The BIS is a committee of central banks and bank supervisors/regulators from the major industrialized countries that develops broad policy guidelines for use by each country’s supervisors in determining the supervisory policies they apply. In 2004, the BIS published a new capital accord to replace its 1988 capital accord. The new capital accord would, among other things, set capital requirements for operational risk and refine the existing capital requirements for credit risk and market risk. Operational risk is defined to mean the risk of direct or indirect loss resulting from inadequate or failed internal processes, people and systems in connection with external events. The 1988 capital accord does not include separate capital requirements for operational risk. The United States federal regulatory authorities are currently expected to release proposed rules to implement the BIS’s new capital accord in the first quarter of 2006. The Corporation cannot predict the timing or final form of the United States rules implementing the new capital accord and their impact on the Corporation. The new capital requirements that may arise from the final rules could increase the minimum capital requirements applicable to Cullen/Frost and its subsidiaries.

      Substantially all of the deposits of Frost Bank are insured up to applicable limits by the Bank Insurance Fund (“BIF”) of the FDIC and are subject to deposit insurance assessments to maintain the BIF. The FDIC utilizes a risk-based assessment system that imposes insurance premiums based upon a matrix that takes into account a bank’s capital level and supervisory rating. Frost Bank was not required to pay any deposit insurance premiums in 2005; however, it is possible that the FDIC could impose assessment rates in the future in connection with declines in the insurance funds or increases in the amount of insurance coverage. An increase in the assessment rate could have a material adverse effect on the Corporation’s earnings, depending on the amount of the increase. During 2005, Frost Bank paid $1.1 million in Financing Corporation (“FICO”) assessments related to outstanding FICO bonds to the FDIC as collection agent. The FICO is a mixed-ownership government corporation established by the Competitive Equality Banking Act of 1987 whose sole purpose was to function as a financing vehicle for the now defunct Federal Savings & Loan Insurance Corporation.

      The FDIA provides that, in the event of the “liquidation or other resolution” of an insured depository institution, the claims of depositors of the institution, including the claims of the FDIC as subrogee of insured depositors, and certain claims for administrative expenses of the FDIC as a receiver, will have priority over other general unsecured claims against the institution. If an insured depository institution fails, insured and uninsured depositors, along with the FDIC, will have priority in payment ahead of unsecured, non-deposit creditors, including the parent bank holding company, with respect to any extensions of credit they have made to such insured depository institution.

      FDIC-insured depository institutions can be held liable for any loss incurred, or reasonably expected to be incurred, by the FDIC due to the default of an FDIC-insured depository institution controlled by the same bank holding company, or for any assistance provided by the FDIC to an FDIC-insured depository institution controlled by the same bank holding company that is in danger of default. “Default” means generally the appointment of a conservator or receiver. “In danger of default” means generally the existence of certain conditions indicating that default is likely to occur in the absence of regulatory assistance.

      The Community Reinvestment Act of 1977 (“CRA”) requires depository institutions to assist in meeting the credit needs of their market areas consistent with safe and sound banking practice. Under the CRA, each

depository institution is required to help meet the credit needs of its market areas by, among other things, providing credit to low- and moderate-income individuals and communities. Depository institutions are periodically examined for compliance with the CRA and are assigned ratings. In order for a financial holding company to commence any new activity permitted by the BHC Act, or to acquire any company engaged in any new activity permitted by the BHC Act, each insured depository institution subsidiary of the financial holding company must have received a rating of at least “satisfactory” in its most recent examination under the CRA. Furthermore, banking regulators take into account CRA ratings when considering approval of a proposed transaction.

      In accordance with the GLB Act, federal banking regulators adopted rules that limit the ability of banks and other financial institutions to disclose non-public information about consumers to nonaffiliated third parties. These limitations require disclosure of privacy policies to consumers and, in some circumstances, allow consumers to prevent disclosure of certain personal information to a nonaffiliated third party. The privacy provisions of the GLB Act affect how consumer information is transmitted through diversified financial companies and conveyed to outside vendors.

      A major focus of governmental policy on financial institutions in recent years has been aimed at combating money laundering and terrorist financing. The USA PATRIOT Act of 2001 (the “USA Patriot Act”) substantially broadened the scope of United States anti-money laundering laws and regulations by imposing significant new compliance and due diligence obligations, creating new crimes and penalties and expanding the extra-territorial jurisdiction of the United States. The United States Treasury Department has issued a number of regulations that apply various requirements of the USA Patriot Act to financial institutions such as Cullen/Frost’s bank and broker-dealer subsidiaries. These regulations impose obligations on financial institutions to maintain appropriate policies, procedures and controls to detect, prevent and report money laundering and terrorist financing and to verify the identity of their customers. Failure of a financial institution to maintain and implement adequate programs to combat money laundering and terrorist financing, or to comply with all of the relevant laws or regulations, could have serious legal and reputational consequences for the institution.

      From time to time, various legislative and regulatory initiatives are introduced in Congress and state legislatures, as well as by regulatory agencies. Such initiatives may include proposals to expand or contract the powers of bank holding companies and depository institutions or proposals to substantially change the financial institution regulatory system. Such legislation could change banking statutes and the operating environment of the Corporation in substantial and unpredictable ways. If enacted, such legislation could increase or decrease the cost of doing business, limit or expand permissible activities or affect the competitive balance among banks, savings associations, credit unions, and other financial institutions. The Corporation cannot predict whether any such legislation will be enacted, and, if enacted, the effect that it, or any implementing regulations, would have on the financial condition or results of operations of the Corporation. A change in statutes, regulations or regulatory policies applicable to Cullen/Frost or any of its subsidiaries could have a material effect on the business of the Corporation.

Employees

       At December 31, 2005, the Corporation employed 3,386 full-time equivalent employees. None of the Corporation’s employees are represented by collective bargaining agreements. The Corporation believes its employee relations to be good.

Executive Officers of the Registrant

       The names, ages as of December 31, 2005, recent business experience and positions or offices held by each of the executive officers of Cullen/Frost are as follows:

      There are no arrangements or understandings between any executive officer of Cullen/Frost and any other person pursuant to which such executive officer was or is to be selected as an officer.

Available Information

       Under the Securities Exchange Act of 1934, Cullen/Frost is required to file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission (“SEC”). You may read and copy any document Cullen/Frost files with the SEC at the SEC’s Public Reference Room at 450 Fifth Street, N.W., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 for further information about the public reference room. The SEC maintains a website at http://www.sec.gov that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC. Cullen/Frost files electronically with the SEC.

      Cullen/Frost makes available, free of charge through its website, its reports on Forms 10-K, 10-Q and 8-K, and amendments to those reports, as soon as reasonably practicable after such reports are filed with or furnished to the SEC. Additionally, the Corporation has adopted and posted on its website a code of ethics that applies to its principal executive officer, principal financial officer and principal accounting officer. The Corporation’s website also includes its corporate governance guidelines and the charters for its audit committee, its compensation and benefits committee, and its corporate governance and nominating committee. The address for the Corporation’s website is http://www.frostbank.com. The Corporation will provide a printed copy of any of the aforementioned documents to any requesting shareholder.

      An investment in the Corporation’s common stock is subject to risks inherent to the Corporation’s business. The material risks and uncertainties that management believes affect the Corporation are described below. Before making an investment decision, you should carefully consider the risks and uncertainties described below together with all of the other information included or incorporated by reference in this report. The risks and uncertainties described below are not the only ones facing the Corporation. Additional risks and uncertainties that management is not aware of or focused on or that management currently deems immaterial may also impair the Corporation’s business operations. This report is qualified in its entirety by these risk factors.

      If any of the following risks actually occur, the Corporation’s financial condition and results of operations could be materially and adversely affected. If this were to happen, the value of the Corporation’s common stock could decline significantly, and you could lose all or part of your investment.

Risks Related To The Corporation’s Business

      The Corporation’s earnings and cash flows are largely dependent upon its net interest income. Net interest income is the difference between interest income earned on interest-earning assets such as loans and securities and interest expense paid on interest-bearing liabilities such as deposits and borrowed funds. Interest rates are highly sensitive to many factors that are beyond the Corporation’s control, including general economic conditions and policies of various governmental and regulatory agencies and, in particular, the Board of Governors of the Federal Reserve System. Changes in monetary policy, including changes in interest rates, could influence not only the interest the Corporation receives on loans and securities and the amount of interest it pays on deposits and borrowings, but such changes could also affect (i) the Corporation’s ability to originate loans and obtain deposits, (ii) the fair value of the Corporation’s financial assets and liabilities, and (iii) the average duration of the Corporation’s mortgage-backed securities portfolio. If the interest rates paid on deposits and other borrowings increase at a faster rate than the interest rates received on loans and other investments, the Corporation’s net interest income, and therefore earnings, could be adversely affected. Earnings could also be adversely affected if the interest rates received on loans and other investments fall more quickly than the interest rates paid on deposits and other borrowings.

      Although management believes it has implemented effective asset and liability management strategies, including the use of derivatives as hedging instruments, to reduce the potential effects of changes in interest rates on the Corporation’s results of operations, any substantial, unexpected, prolonged change in market interest rates could have a material adverse effect on the Corporation’s financial condition and results of operations. See the section captioned “Net Interest Income” in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations located elsewhere in this report for further discussion related to the Corporation’s management of interest rate risk.

      There are inherent risks associated with the Corporation’s lending activities. These risks include, among other things, the impact of changes in interest rates and changes in the economic conditions in the markets

where the Corporation operates as well as those across the State of Texas and the United States. Increases in interest rates and/or weakening economic conditions could adversely impact the ability of borrowers to repay outstanding loans or the value of the collateral securing these loans. The Corporation is also subject to various laws and regulations that affect its lending activities. Failure to comply with applicable laws and regulations could subject the Corporation to regulatory enforcement action that could result in the assessment of significant civil money penalties against the Corporation.

      As of December 31, 2005, approximately 80% of the Corporation’s loan portfolio consisted of commercial and industrial, construction and commercial real estate loans. These types of loans are generally viewed as having more risk of default than residential real estate loans or consumer loans. These types of loans are also typically larger than residential real estate loans and consumer loans. Because the Corporation’s loan portfolio contains a significant number of commercial and industrial, construction and commercial real estate loans with relatively large balances, the deterioration of one or a few of these loans could cause a significant increase in non-performing loans. An increase in non-performing loans could result in a net loss of earnings from these loans, an increase in the provision for possible loan losses and an increase in loan charge-offs, all of which could have a material adverse effect on the Corporation’s financial condition and results of operations. See the section captioned “Loans” in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations located elsewhere in this report for further discussion related to commercial and industrial, construction and commercial real estate loans.

      The Corporation maintains an allowance for possible loan losses, which is a reserve established through a provision for possible loan losses charged to expense, that represents management’s best estimate of probable losses that have been incurred within the existing portfolio of loans. The allowance, in the judgment of management, is necessary to reserve for estimated loan losses and risks inherent in the loan portfolio. The level of the allowance reflects management’s continuing evaluation of industry concentrations; specific credit risks; loan loss experience; current loan portfolio quality; present economic, political and regulatory conditions and unidentified losses inherent in the current loan portfolio. The determination of the appropriate level of the allowance for possible loan losses inherently involves a high degree of subjectivity and requires the Corporation to make significant estimates of current credit risks and future trends, all of which may undergo material changes. Changes in economic conditions affecting borrowers, new information regarding existing loans, identification of additional problem loans and other factors, both within and outside of the Corporation’s control, may require an increase in the allowance for possible loan losses. In addition, bank regulatory agencies periodically review the Corporation’s allowance for loan losses and may require an increase in the provision for possible loan losses or the recognition of further loan charge-offs, based on judgments different than those of management. In addition, if charge-offs in future periods exceed the allowance for possible loan losses, the Corporation will need additional provisions to increase the allowance for possible loan losses. Any increases in the allowance for possible loan losses will result in a decrease in net income and, possibly, capital, and may have a material adverse effect on the Corporation’s financial condition and results of operations. See the section captioned “Allowance for Possible Loan Losses” in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations located elsewhere in this report for further discussion related to the Corporation’s process for determining the appropriate level of the allowance for possible loan losses.

      A significant portion of the Corporation’s loan portfolio is secured by real property. During the ordinary course of business, the Corporation may foreclose on and take title to properties securing certain loans. In doing so, there is a risk that hazardous or toxic substances could be found on these properties. If hazardous or toxic substances are found, the Corporation may be liable for remediation costs, as well as for personal injury and property damage. Environmental laws may require the Corporation to incur substantial expenses and may materially reduce the affected property’s value or limit the Corporation’s ability to use or sell the affected property. In addition, future laws or more stringent interpretations or enforcement policies with respect to existing laws may increase the Corporation’s exposure to environmental liability. Although the Corporation

has policies and procedures to perform an environmental review before initiating any foreclosure action on real property, these reviews may not be sufficient to detect all potential environmental hazards. The remediation costs and any other financial liabilities associated with an environmental hazard could have a material adverse effect on the Corporation’s financial condition and results of operations.

      The Corporation’s success depends primarily on the general economic conditions of the State of Texas and the specific local markets in which the Corporation operates. Unlike larger national or other regional banks that are more geographically diversified, the Corporation provides banking and financial services to customers primarily in the Texas metropolitan areas of Austin, Boerne, Corpus Christi, Dallas, Fort Worth, Galveston, Harlingen, Houston, McAllen, New Braunfels, San Antonio and San Marcos. The local economic conditions in these areas have a significant impact on the demand for the Corporation’s products and services as well as the ability of the Corporation’s customers to repay loans, the value of the collateral securing loans and the stability of the Corporation’s deposit funding sources. A significant decline in general economic conditions, caused by inflation, recession, acts of terrorism, outbreak of hostilities or other international or domestic occurrences, unemployment, changes in securities markets or other factors could impact these local economic conditions and, in turn, have a material adverse effect on the Corporation’s financial condition and results of operations.

      The Corporation faces substantial competition in all areas of its operations from a variety of different competitors, many of which are larger and may have more financial resources. Such competitors primarily include national, regional, and community banks within the various markets the Corporation operates. Additionally, various out-of-state banks have begun to enter or have announced plans to enter the market areas in which the Corporation currently operates. The Corporation also faces competition from many other types of financial institutions, including, without limitation, savings and loans, credit unions, finance companies, brokerage firms, insurance companies, factoring companies and other financial intermediaries. The financial services industry could become even more competitive as a result of legislative, regulatory and technological changes and continued consolidation. Banks, securities firms and insurance companies can merge under the umbrella of a financial holding company, which can offer virtually any type of financial service, including banking, securities underwriting, insurance (both agency and underwriting) and merchant banking. Also, technology has lowered barriers to entry and made it possible for non-banks to offer products and services traditionally provided by banks, such as automatic transfer and automatic payment systems. Many of the Corporation’s competitors have fewer regulatory constraints and may have lower cost structures. Additionally, due to their size, many competitors may be able to achieve economies of scale and, as a result, may offer a broader range of products and services as well as better pricing for those products and services than the Corporation can.

      The Corporation’s ability to compete successfully depends on a number of factors, including, among other things:

      Failure to perform in any of these areas could significantly weaken the Corporation’s competitive position, which could adversely affect the Corporation’s growth and profitability, which, in turn, could have a material adverse effect on the Corporation’s financial condition and results of operations.

      The Corporation, primarily through Cullen/Frost, Frost Bank and certain non-bank subsidiaries, is subject to extensive federal and state regulation and supervision. Banking regulations are primarily intended to protect depositors’ funds, federal deposit insurance funds and the banking system as a whole, not shareholders. These regulations affect the Corporation’s lending practices, capital structure, investment practices, dividend policy and growth, among other things. Congress and federal regulatory agencies continually review banking laws, regulations and policies for possible changes. Changes to statutes, regulations or regulatory policies, including changes in interpretation or implementation of statutes, regulations or policies, could affect the Corporation in substantial and unpredictable ways. Such changes could subject the Corporation to additional costs, limit the types of financial services and products the Corporation may offer and/or increase the ability of non-banks to offer competing financial services and products, among other things. Failure to comply with laws, regulations or policies could result in sanctions by regulatory agencies, civil money penalties and/or reputation damage, which could have a material adverse effect on the Corporation’s business, financial condition and results of operations. While the Corporation has policies and procedures designed to prevent any such violations, there can be no assurance that such violations will not occur. See the section captioned “Supervision and Regulation” in Item 1. Business and Note 12 — Regulatory Matters in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which are located elsewhere in this report.

      Management regularly reviews and updates the Corporation’s internal controls, disclosure controls and procedures, and corporate governance policies and procedures. Any system of controls, however well designed and operated, is based in part on certain assumptions and can provide only reasonable, not absolute, assurances that the objectives of the system are met. Any failure or circumvention of the Corporation’s controls and procedures or failure to comply with regulations related to controls and procedures could have a material adverse effect on the Corporation’s business, results of operations and financial condition.

      From time to time, the Corporation may implement new lines of business or offer new products and services within existing lines of business. There are substantial risks and uncertainties associated with these efforts, particularly in instances where the markets are not fully developed. In developing and marketing new lines of business and/or new products and services the Corporation may invest significant time and resources. Initial timetables for the introduction and development of new lines of business and/or new products or services may not be achieved and price and profitability targets may not prove feasible. External factors, such as compliance with regulations, competitive alternatives, and shifting market preferences, may also impact the successful implementation of a new line of business or a new product or service. Furthermore, any new line of business and/or new product or service could have a significant impact on the effectiveness of the Corporation’s system of internal controls. Failure to successfully manage these risks in the development and implementation of new lines of business or new products or services could have a material adverse effect on the Corporation’s business, results of operations and financial condition.

      Cullen/Frost is a separate and distinct legal entity from its subsidiaries. It receives substantially all of its revenue from dividends from its subsidiaries. These dividends are the principal source of funds to pay dividends on the Corporation’s common stock and interest and principal on Cullen/Frost’s debt. Various federal and/or state laws and regulations limit the amount of dividends that Frost Bank and certain non-bank subsidiaries may pay to Cullen/Frost. Also, Cullen/Frost’s right to participate in a distribution of assets upon

a subsidiary’s liquidation or reorganization is subject to the prior claims of the subsidiary’s creditors. In the event Frost Bank is unable to pay dividends to Cullen/Frost, Cullen/Frost may not be able to service debt, pay obligations or pay dividends on the Corporation’s common stock. The inability to receive dividends from Frost Bank could have a material adverse effect on the Corporation’s business, financial condition and results of operations. See the section captioned “Supervision and Regulation” in Item 1. Business and Note 12 — Regulatory Matters in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which are located elsewhere in this report.

      The Corporation seeks merger or acquisition partners that are culturally similar and have experienced management and possess either significant market presence or have potential for improved profitability through financial management, economies of scale or expanded services. Acquiring other banks, businesses, or branches involves various risks commonly associated with acquisitions, including, among other things:

      The Corporation regularly evaluates merger and acquisition opportunities and conducts due diligence activities related to possible transactions with other financial institutions and financial services companies. As a result, merger or acquisition discussions and, in some cases, negotiations may take place and future mergers or acquisitions involving cash, debt or equity securities may occur at any time. Acquisitions typically involve the payment of a premium over book and market values, and, therefore, some dilution of the Corporation’s tangible book value and net income per common share may occur in connection with any future transaction. Furthermore, failure to realize the expected revenue increases, cost savings, increases in geographic or product presence, and/or other projected benefits from an acquisition could have a material adverse effect on the Corporation’s financial condition and results of operations.

      During 2005, the Corporation acquired Horizon Capital Bank (Houston market area) and announced definitive agreements to acquire Texas Community Bancshares, Inc. (Dallas market area) and Alamo Corporation of Texas (Rio Grande Valley market area). Details of these transactions are presented in Note 2 — Mergers and Acquisitions in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, which is located elsewhere in this report.

The Corporation May Not Be Able To Attract and Retain Skilled People

      The Corporation’s success depends, in large part, on its ability to attract and retain key people. Competition for the best people in most activities engaged in by the Corporation can be intense and the Corporation may not be able to hire people or to retain them. The unexpected loss of services of one or more of the Corporation’s key personnel could have a material adverse impact on the Corporation’s business because of their skills, knowledge of the Corporation’s market, years of industry experience and the difficulty of promptly finding qualified replacement personnel. The Corporation does not currently have employment agreements or non-competition agreements with any of its senior officers.

      The Corporation relies heavily on communications and information systems to conduct its business. Any failure, interruption or breach in security of these systems could result in failures or disruptions in the Corporation’s customer relationship management, general ledger, deposit, loan and other systems. While the Corporation has policies and procedures designed to prevent or limit the effect of the failure, interruption or security breach of its information systems, there can be no assurance that any such failures, interruptions or security breaches will not occur or, if they do occur, that they will be adequately addressed. The occurrence of any failures, interruptions or security breaches of the Corporation’s information systems could damage the Corporation’s reputation, result in a loss of customer business, subject the Corporation to additional regulatory scrutiny, or expose the Corporation to civil litigation and possible financial liability, any of which could have a material adverse effect on the Corporation’s financial condition and results of operations.

      The financial services industry is continually undergoing rapid technological change with frequent introductions of new technology-driven products and services. The effective use of technology increases efficiency and enables financial institutions to better serve customers and to reduce costs. The Corporation’s future success depends, in part, upon its ability to address the needs of its customers by using technology to provide products and services that will satisfy customer demands, as well as to create additional efficiencies in the Corporation’s operations. Many of the Corporation’s competitors have substantially greater resources to invest in technological improvements. The Corporation may not be able to effectively implement new technology-driven products and services or be successful in marketing these products and services to its customers. Failure to successfully keep pace with technological change affecting the financial services industry could have a material adverse impact on the Corporation’s business and, in turn, the Corporation’s financial condition and results of operations.

      From time to time, customers make claims and take legal action pertaining to the Corporation’s performance of its fiduciary responsibilities. Whether customer claims and legal action related to the Corporation’s performance of its fiduciary responsibilities are founded or unfounded, if such claims and legal actions are not resolved in a manner favorable to the Corporation they may result in significant financial liability and/or adversely affect the market perception of the Corporation and its products and services as well as impact customer demand for those products and services. Any financial liability or reputation damage could have a material adverse effect on the Corporation’s business, which, in turn, could have a material adverse effect on the Corporation’s financial condition and results of operations.

      Severe weather, natural disasters, acts of war or terrorism and other adverse external events could have a significant impact on the Corporation’s ability to conduct business. Such events could affect the stability of the Corporation’s deposit base, impair the ability of borrowers to repay outstanding loans, impair the value of collateral securing loans, cause significant property damage, result in loss of revenue and/or cause the Corporation to incur additional expenses. For example, during 2005, hurricanes Katrina and Rita made landfall and subsequently caused extensive flooding and destruction along the coastal areas of the Gulf of Mexico, including communities where the Corporation conducts business. Operations in several of the Company’s markets were disrupted by both the evacuation of large portions of the population as well as damage and or lack of access to the Company’s banking and operation facilities. While the impact of these hurricanes did not significantly affect the Corporation, other severe weather or natural disasters, acts of war or terrorism or other adverse external events may occur in the future. Although management has established disaster recovery policies and procedures, the occurrence of any such event could have a material adverse effect on the Corporation’s business, which, in turn, could have a material adverse effect on the Corporation’s financial condition and results of operations.

Risks Associated With The Corporation’s Common Stock

      Stock price volatility may make it more difficult for you to resell your common stock when you want and at prices you find attractive. The Corporation’s stock price can fluctuate significantly in response to a variety of factors including, among other things:

      General market fluctuations, industry factors and general economic and political conditions and events, such as economic slowdowns or recessions, interest rate changes or credit loss trends, could also cause the Corporation’s stock price to decrease regardless of operating results.

      Although the Corporation’s common stock is listed for trading on the New York Stock Exchange (NYSE), the trading volume in its common stock is less than that of other larger financial services companies. A public trading market having the desired characteristics of depth, liquidity and orderliness depends on the presence in the marketplace of willing buyers and sellers of the Corporation’s common stock at any given time. This presence depends on the individual decisions of investors and general economic and market conditions over which the Corporation has no control. Given the lower trading volume of the Corporation’s common stock, significant sales of the Corporation’s common stock, or the expectation of these sales, could cause the Corporation’s stock price to fall.

      The Corporation’s common stock is not a bank deposit and, therefore, is not insured against loss by the Federal Deposit Insurance Corporation (FDIC), any other deposit insurance fund or by any other public or private entity. Investment in the Corporation’s common stock is inherently risky for the reasons described in this “Risk Factors” section and elsewhere in this report and is subject to the same market forces that affect the price of common stock in any company. As a result, if you acquire the Corporation’s common stock, you may lose some or all of your investment.

      Provisions of the Corporation’s articles of incorporation and by-laws, federal banking laws, including regulatory approval requirements, and the Corporation’s stock purchase rights plan could make it more

difficult for a third party to acquire the Corporation, even if doing so would be perceived to be beneficial to the Corporation’s shareholders. The combination of these provisions effectively inhibits a non-negotiated merger or other business combination, which, in turn, could adversely affect the market price of the Corporation’s common stock.

Risks Associated With The Corporation’s Industry

      The Corporation’s operations and profitability are impacted by general business and economic conditions in the United States and abroad. These conditions include short-term and long-term interest rates, inflation, money supply, political issues, legislative and regulatory changes, fluctuations in both debt and equity capital markets, broad trends in industry and finance, and the strength of the U.S. economy and the local economies in which the Corporation operates, all of which are beyond the Corporation’s control. A deterioration in economic conditions could result in an increase in loan delinquencies and non-performing assets, decreases in loan collateral values and a decrease in demand for the Corporation’s products and services, among other things, any of which could have a material adverse impact on the Corporation’s financial condition and results of operations.

      In deciding whether to extend credit or enter into other transactions, the Corporation may rely on information furnished by or on behalf of customers and counterparties, including financial statements, credit reports and other financial information. The Corporation may also rely on representations of those customers, counterparties or other third parties, such as independent auditors, as to the accuracy and completeness of that information. Reliance on inaccurate or misleading financial statements, credit reports or other financial information could have a material adverse impact on the Corporation’s business and, in turn, the Corporation’s financial condition and results of operations.

      Technology and other changes are allowing parties to complete financial transactions that historically have involved banks through alternative methods. For example, consumers can now maintain funds that would have historically been held as bank deposits in brokerage accounts or mutual funds. Consumers can also complete transactions such as paying bills and/or transferring funds directly without the assistance of banks. The process of eliminating banks as intermediaries, known as “disintermediation,” could result in the loss of fee income, as well as the loss of customer deposits and the related income generated from those deposits. The loss of these revenue streams and the lower cost deposits as a source of funds could have a material adverse effect on the Corporation’s financial condition and results of operations.

ITEM 1B.     UNRESOLVED STAFF COMMENTS

      None

      The Corporation’s primary offices are located in downtown San Antonio, Texas. These facilities, which are owned by the Corporation, house the Corporation’s executive and primary administrative offices, as well as the principal banking headquarters of Frost Bank. The Corporation also owns or leases other facilities within its primary market areas of Austin, Boerne, Corpus Christi, Dallas, Fort Worth, Galveston, Harlingen, Houston, McAllen, New Braunfels, San Antonio and San Marcos. The Corporation considers its properties to be suitable and adequate for its present needs.

      The Corporation is subject to various claims and legal actions that have arisen in the normal course of conducting business. Management does not expect the ultimate disposition of these matters to have a material adverse impact on the Corporation’s financial statements.

      No matters were submitted to a vote of security holders during the fourth quarter of 2005.

PART II

      The Corporation’s common stock is traded on The New York Stock Exchange, Inc. (“NYSE”) under the symbol “CFR”. The tables below set forth for each quarter of 2005 and 2004 the high and low intra-day sales prices per share of Cullen/Frost’s common stock as reported by the NYSE and the cash dividends declared per share.

      As of December 31, 2005, there were 54,482,735 shares of the Corporation’s common stock outstanding held by 1,943 holders of record. The closing price per share of common stock on December 30, 2005, the last trading day of the Corporation’s fiscal year, was $53.68.

      The Corporation’s management is currently committed to continuing to pay regular cash dividends; however, there can be no assurance as to future dividends because they are dependent on the Corporation’s future earnings, capital requirements and financial condition. See the section captioned “Supervision and Regulation” included in Item 1. Business, the section captioned “Capital and Liquidity” included in Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations and Note 12 — Regulatory Matters in the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data, all of which are included elsewhere in this report.

      Information regarding stock-based compensation awards outstanding and available for future grants as of December 31, 2005, segregated between stock-based compensation plans approved by shareholders and stock-based compensation plans not approved by shareholders, is presented in the table below. Additional information regarding stock-based compensation plans is presented in Note 13 — Employee Benefit Plans in

the notes to consolidated financial statements included in Item 8. Financial Statements and Supplementary Data located elsewhere in this report.

      During 2005, the Corporation maintained a stock repurchase plan authorized by the Corporation’s board of directors. Stock repurchase plans allow the Corporation to proactively manage its capital position and return excess capital to shareholders. Shares purchased under such plans also provide the Corporation with shares of common stock necessary to satisfy obligations related to stock compensation awards. The Corporation’s board of directors approved the current stock repurchase plan on April 29, 2004. Under this plan, the Corporation is authorized to repurchase up to 2.1 million shares of its common stock from time to time over a two-year period ending April 29, 2006 in the open market or through private transactions. Under the plan, during the 2005, the Corporation repurchased 300 thousand shares at a cost of $14.4 million, all of which occurred during the first quarter. From the inception of the Plan through December 31, 2005, the Corporation has repurchased a total of 833.2 thousand shares under this plan at a cost of $39.9 million.

      The Corporation previously maintained a stock repurchase plan implemented in October 2003. This plan, which was completed in 2004, authorized the Corporation to repurchase from time to time up to 1.2 million shares of its common stock over a two-year period ending in October 2005 in the open market or through private transactions. Under the plan, during 2003, the Corporation repurchased 267.9 thousand shares at a cost of $10.7 million. During 2004, the Corporation repurchased the remaining 932.1 thousand shares authorized under the plan at a cost of $39.7 million.

      The following table provides information with respect to purchases made by or on behalf of the Corporation or any “affiliated purchaser” (as defined in Rule 10b-18(a)(3) under the Securities Exchange Act of 1934), of the Corporation’s common stock during the fourth quarter of 2005.

      The following consolidated selected financial data is derived from the Corporation’s audited financial statements as of and for the five years ended December 31, 2005. The following consolidated financial data should be read in conjunction with Management’s Discussion and Analysis of Financial Condition and Results of Operations and the Consolidated Financial Statements and related notes included elsewhere in this report. All of the Corporation’s acquisitions during the five years ended December 31, 2005 were accounted for using the purchase method. Accordingly, the operating results of the acquired companies are included with the Corporation’s results of operations since their respective dates of acquisition. Dollar amounts are in thousands, except per share data.

Selected Financial Data (continued)

Selected Financial Data (continued)

      The following tables set forth unaudited consolidated selected quarterly statement of operations data for the years ended December 31, 2005 and 2004. Dollar amounts are in thousands, except per share data.

Forward-Looking Statements and Factors that Could Affect Future Results

       Certain statements contained in this Annual Report on Form 10-K that are not statements of historical fact constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 (the “Act”), notwithstanding that such statements are not specifically identified. In addition, certain statements may be contained in the Corporation’s future filings with the SEC, in press releases, and in oral and written statements made by or with the approval of the Corporation that are not statements of historical fact and constitute forward-looking statements within the meaning of the Act. Examples of forward-looking statements include, but are not limited to: (i) projections of revenues, expenses, income or loss, earnings or loss per share, the payment or nonpayment of dividends, capital structure and other financial items; (ii) statements of plans, objectives and expectations of Cullen/ Frost or its management or Board of Directors, including those relating to products or services; (iii) statements of future economic performance; and (iv) statements of assumptions underlying such statements. Words such as “believes”, “anticipates”, “expects”, “intends”, “targeted”, “continue”, “remain”, “will”, “should”, “may” and other similar expressions are intended to identify forward-looking statements but are not the exclusive means of identifying such statements.

      Forward-looking statements involve risks and uncertainties that may cause actual results to differ materially from those in such statements. Factors that could cause actual results to differ from those discussed in the forward-looking statements include, but are not limited to:

      Forward-looking statements speak only as of the date on which such statements are made. The Corporation undertakes no obligation to update any forward-looking statement to reflect events or circumstances after the date on which such statement is made, or to reflect the occurrence of unanticipated events.

The Corporation

       Cullen/Frost Bankers, Inc. (Cullen/Frost) is a financial holding company and a bank holding company headquartered in San Antonio, Texas that provides, through its wholly owned subsidiaries (collectively referred to as the “Corporation”), a broad array of products and services throughout 12 Texas markets. The Corporation offers commercial and consumer banking services, as well as trust and investment management, investment banking, insurance brokerage, leasing, asset-based lending, treasury management and item processing services.

Application of Critical Accounting Policies and Accounting Estimates

       The accounting and reporting policies followed by the Corporation conform, in all material respects, to accounting principles generally accepted in the United States. The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. While the Corporation bases estimates on historical experience, current information and other factors deemed to be relevant, actual results could differ from those estimates.

      The Corporation considers accounting estimates to be critical to reported financial results if (i) the accounting estimate requires management to make assumptions about matters that are highly uncertain and (ii) different estimates that management reasonably could have used for the accounting estimate in the current period, or changes in the accounting estimate that are reasonably likely to occur from period to period, could have a material impact on the Corporation’s financial statements. Accounting policies related to the allowance for possible loan losses are considered to be critical, as these policies involve considerable subjective judgment and estimation by management. The Corporation also considers accounting policies related to stock-based compensation to be critical due to the continuously evolving standards, changes to which will materially impact the way the Corporation accounts for stock options beginning January 1, 2006. Critical accounting policies, and the Corporation’s procedures related to these policies, are described below. Also see Note 1 — Summary of Significant Accounting Policies in the accompanying notes to consolidated financial statements included elsewhere in this report.

      Allowance for Possible Loan Losses. The allowance for possible loan losses is a reserve established through a provision for possible loan losses charged to expense, which represents management’s best estimate of probable losses that have been incurred within the existing portfolio of loans. The allowance, in the judgment of management, is necessary to reserve for estimated loan losses and risks inherent in the loan portfolio. The Corporation’s allowance for possible loan loss methodology is based on guidance provided in SEC Staff Accounting Bulletin No. 102, “Selected Loan Loss Allowance Methodology and Documentation Issues” and includes allowance allocations calculated in accordance with Statement of Financial Accounting Standards (SFAS) No. 114, “Accounting by Creditors for Impairment of a Loan,” as amended by SFAS 118,

and allowance allocations determined in accordance with SFAS No. 5, “Accounting for Contingencies.” The level of the allowance reflects management’s continuing evaluation of industry concentrations, specific credit risks, loan loss experience, current loan portfolio quality, present economic, political and regulatory conditions and unidentified losses inherent in the current loan portfolio. Portions of the allowance may be allocated for specific credits; however, the entire allowance is available for any credit that, in management’s judgment, should be charged off. While management utilizes its best judgment and information available, the ultimate adequacy of the allowance is dependent upon a variety of factors beyond the Corporation’s control, including the performance of the Corporation’s loan portfolio, the economy, changes in interest rates and the view of the regulatory authorities toward loan classifications. See the section captioned “Allowance for Possible Loan Losses” elsewhere in this discussion for further details of the risk factors considered by management in estimating the necessary level of the allowance for possible loan losses.

      Stock-based Compensation. The Corporation accounts for stock-based employee compensation plans based on the “intrinsic value method” provided in Accounting Principles Board Opinion (APB) No. 25, “Accounting for Stock Issued to Employees,” and related Interpretations. Because the exercise price of the Corporation’s employee stock options equals the market price of the underlying stock on the measurement date, which is generally the date of grant, no compensation expense is recognized on options granted. Compensation expense for stock awards is based on the market price of the stock on the measurement date, which is generally the date of grant, and is recognized ratably over the service period of the award.

      SFAS No. 123, “Accounting for Stock-Based Compensation,” as amended by SFAS 148, requires pro forma disclosures of net income and earnings per share for companies not adopting its fair value accounting method for stock-based employee compensation. The pro forma disclosures presented in Note 13 — Employee Benefit Plans in the accompanying notes to consolidated financial statements included elsewhere in this report use the fair value method of SFAS 123 to measure compensation expense for stock-based employee compensation plans. The fair value of stock options granted was estimated at the measurement date, which is generally the date of grant, using the Black-Scholes option-pricing model. This model was developed for use in estimating the fair value of publicly traded options that have no vesting restrictions and are fully transferable. Additionally, the model requires the input of highly subjective assumptions. Because the Corporation’s employee stock options have characteristics significantly different from those of publicly traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the Black-Scholes option-pricing model does not necessarily provide a reliable single measure of the fair value of the Corporation’s employee stock options.

      In December 2004, the Financial Accounting Standards Board (FASB) issued SFAS No. 123, “Share-Based Payment (Revised 2004).” Among other things, SFAS 123R eliminates the ability to account for stock-based compensation using APB 25 and requires that such transactions be recognized as compensation cost in the income statement based on their fair values on the date of the grant. SFAS 123R is effective for the Corporation on January 1, 2006. See Note 21 — New Accounting Standards in the accompanying notes to consolidated financial statements included elsewhere in this report.

Overview

       The following discussion and analysis presents the more significant factors affecting the Corporation’s financial condition as of December 31, 2005 and 2004 and results of operations for each of the three years in the period ended December 31, 2005. This discussion and analysis should be read in conjunction with the Corporation’s consolidated financial statements, notes thereto and other financial information appearing elsewhere in this report. All of the Corporation’s acquisitions during the reported periods were accounted for as purchase transactions, and as such, their related results of operations are included from the date of acquisition. None of the acquisitions had a material impact on the Corporation’s financial statements. See Note 2 — Mergers and Acquisitions in the accompanying notes to consolidated financial statements included elsewhere in this report.

      Taxable-equivalent adjustments are the result of increasing income from tax-free loans and investments by an amount equal to the taxes that would be paid if the income were fully taxable based on a 35% federal tax rate, thus making tax-exempt yields comparable to taxable asset yields.

      Dollar amounts in tables are stated in thousands, except for per share amounts.

Results of Operations

       Net income totaled $165.4 million, or $3.07 diluted per common share, in 2005 compared to $141.3 million, or $2.66 diluted per common share, in 2004 and $130.5 million, or $2.48 diluted per common share, in 2003. Selected income statement data, returns on average assets and average equity and dividends per share for the comparable periods were as follows:

      Net income for 2005 increased $24.1 million, or 17.1%, compared to 2004. The increase was primarily due to a $59.8 million increase in net interest income and a $5.3 million increase in non-interest income. The impact of these items was partly offset by a $22.0 million increase in non-interest expense, a $11.3 million increase in income tax expense and a $7.8 million increase in the provision for possible loan losses. Net income for 2004 increased $10.8 million, or 8.3%, compared to 2003. The increase was primarily due to a $17.7 million increase in net interest income, a $9.7 million increase in non-interest income and an $8.0 million decrease in the provision for possible loan losses. The impact of these items was partly offset by a $19.0 million increase in non-interest expense and a $5.7 million increase in income tax expense.

      Details of the changes in the various components of net income are further discussed below.

Net Interest Income

       Net interest income is the difference between interest income on earning assets, such as loans and securities, and interest expense on liabilities, such as deposits and borrowings, which are used to fund those assets. Net interest income is the Corporation’s largest source of revenue, representing 62.9% of total revenue during 2005. Net interest margin is the taxable-equivalent net interest income as a percentage of average earning assets for the period. The level of interest rates and the volume and mix of earning assets and interest-bearing liabilities impact net interest income and net interest margin.

      The Federal Reserve Board influences the general market rates of interest, including the deposit and loan rates offered by many financial institutions. The Corporation’s loan portfolio is significantly affected by changes in the prime interest rate. The prime interest rate, which is the rate offered on loans to borrowers with strong credit, began 2003 at 4.25% and decreased 25 basis points at the end of the second quarter and ended the year at 4.00%. During 2004, the prime rate increased 25 basis points at end of the second quarter, 50 basis points during the third quarter and 50 basis points during the fourth quarter and ended the year at 5.25%. During 2005, the prime interest rate increased 50 basis points in each of the four quarters to end the year at 7.25%. The federal funds rate, which is the cost of immediately available overnight funds, fluctuated in a similar manner. It began 2003 at 1.25% and decreased 25 basis points at the end of the second quarter and ended the year at 1.00%. During 2004, the federal funds rate increased 25 basis points at the end of the second quarter, 50 basis points during the third quarter and 50 basis points during the fourth quarter to end the year at 2.25%. During 2005, the federal funds rate increased 50 basis points in each of the four quarters to end the year at 4.25%.

      The Corporation’s balance sheet is asset sensitive, meaning that earning assets generally reprice more quickly than interest-bearing liabilities. Therefore, the Corporation’s net interest margin is likely to increase in sustained periods of rising interest rates and decrease in sustained periods of declining interest rates. The Corporation is primarily funded by core deposits, with non-interest-bearing demand deposits historically being a significant source of funds. This lower-cost funding base is expected to have a positive impact on the Corporation’s net interest income and net interest margin in a rising interest rate environment. The Corporation expects the upward trend in the prime interest rate and the federal funds rate that began in 2004 to continue into the near future; however, there can be no assurance to that effect as fluctuations in market interest rates are dependent upon a variety of factors that are beyond the Corporation’s control. Further analysis of the components of the Corporation’s net interest margin is presented below.

      The following table presents the changes in taxable-equivalent net interest income and identifies the changes due to differences in the average volume of earning assets and interest-bearing liabilities and the changes due to changes in the average interest rate on those assets and liabilities. The changes in net interest income due to changes in both average volume and average interest rate have been allocated to the average volume change or the average interest rate change in proportion to the absolute amounts of the change in each. The Corporation’s consolidated average balance sheets along with an analysis of taxable-equivalent net interest income are presented on pages 108 and 109 of this report.