REGISTRATION RIGHTS AND LOCK-UP AGREEMENT

     This Registration Rights Agreement (this Agreement) is entered into as of July 14, 2006 by and among Archstone-Smith Trust, a Maryland real estate investment trust (the Trust), and Archstone-Smith Operating Trust, a Maryland real estate investment trust (the Company), for itself and for the benefit of the Holders (as hereinafter defined).

     WHEREAS, pursuant to the terms of the Third Supplemental Indenture dated as of July 14, 2006 to the indenture dated as of February 1, 1994, as supplemented by the First Supplemental Indenture, dated as of February 2, 1994, and the Second Supplemental Indenture, dated as of August 2, 2004, between the Company and the U.S. Bank National Association (as successor in interest to State Street Bank and Trust Company), as trustee (the Indenture) pursuant to which the Company issued $575,000,000 principal amount of its 4.00% Exchangeable Senior Notes due 2036 (the Notes), as an inducement for the Holders to purchase Notes, the Trust hereby grants certain registration rights to the Company for the benefit of the Holders with respect to common shares of beneficial interest, par value $0.01 per share (the Common Shares), of the Trust that may in the future be issued to the Holders by the Trust on account of Notes, if such Common Shares when so issued are restricted securities under the Securities Act of 1933, as amended (Restricted Shares), consisting of either (1) Restricted Shares delivered to the Holders by the Company pursuant to the Indenture on account of Notes, or (2) Restricted Shares issued by the Trust upon conversion into Common Shares of Units (as hereinafter defined) issued by the Company to the Holders pursuant to the Indenture on account of Notes, whether by exercise by the Holders of a redemption right or otherwise pursuant to the Company Agreement;

     NOW, THEREFORE, in consideration of the foregoing, the mutual promises and agreements set forth herein, and other valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto hereby agree as follows:

     1. Certain Definitions

     As used in this Agreement, in addition to the other terms defined herein, the following capitalized defined terms shall have the following meanings:

     Affiliate shall mean a Person that directly, or indirectly though one or more intermediaries, controls, is controlled by, or is under common control with a specified Person.

     Common Shares shall have the meaning set forth in the preamble to this Agreement.

     Company shall have the meaning set forth in the preamble to this Agreement.

     Company Offering shall have the meaning set forth in Section 8(c) hereof.

     Demand Registration shall have the meaning set forth in Section 2(b) hereof.

     Exchange Act shall mean the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder.

     Fair Market Value shall mean the closing sales price, or the closing sales bid if no sales were reported, of the Common Shares as quoted on the NYSE or such other national securities exchange on which the Common Shares are listed on the date immediately preceding the date of calculation or if there are no sales or bids for such date, then for the last preceding business day for such sales or bids, as reported in The Wall Street Journal or similar publication.

     Filing Date shall have the meaning set forth in Section 2(a) hereof.

     Holder or Holders shall mean the beneficial owners from time to time of the Notes and the beneficial owners from time to time of the Restricted Shares or Restricted Units issued on account of Notes pursuant to the Indenture.

     Indemnitee shall have the meaning set forth in Section 6 hereof.

     Indenture shall have the meaning set forth in the preamble to this Agreement.

     NASD shall mean the National Association of Securities Dealers, Inc.

     Notes shall have the meaning set forth in the preamble to this Agreement.

     NYSE shall mean the New York Stock Exchange.

     Notice Holder shall mean, on any date, any Holder that has delivered to the Trust on or prior to such date a duly executed and completed Notice and Questionnaire.

     Notice and Questionnaire shall mean a written notice and questionnaire containing all material information required to be disclosed with respect to such Holder as a selling stockholder in a Resale Shelf Registration Statement under the Securities Act.

     Offering Blackout Period shall have the meaning set forth in Section 8(c) hereof.

     Partnership shall have the meaning set forth in the recitals to this Agreement.

     Partnership Agreement shall mean the agreement of limited partnership of BPLP, as amended from time to time.

     Person shall mean an individual, partnership, corporation, trust, or unincorporated organization, or a government or agency or political subdivision thereof.

     Prospectus shall mean the prospectus included in a Registration Statement, including any preliminary prospectus, as amended or supplemented by any prospectus supplement with respect to the terms of the offering of any portion of the Registrable Shares covered by such Registration Statement, and by all other amendments and supplements to such prospectus, including post-effective amendments, and in each case including all material incorporated by reference therein.