Exhibit 15.1

The Board of Trustees
Archstone-Smith Trust:

     With respect to Archstone-Smith Operating Trust’s Registration Statement on Form S-3 (File No. 333-133285), we acknowledge our awareness of the use therein of our report dated May 9, 2006, related to our review of interim financial information.

     Pursuant to Rule 436 under the Securities Act of 1933 (the Act), such report is not considered a part of a registration statement prepared or certified by an accountant, or a report prepared or certified by an accountant within the meaning of Sections 7 and 11 of the Act.

/s/ KPMG LLP

Denver, Colorado

July 10, 2006