Exhibit 5.1
                                                                     -----------


                          GOODWIN, PROCTER & HOAR LLP
                               COUNSELORS AT LAW
                                EXCHANGE PLACE
                       BOSTON, MASSACHUSETTS 02109-2881


                                 June 30, 2000



Boston Properties, Inc.
800 Boylston Street, Suite 400
Boston, Massachusetts 02199-8001

Ladies and Gentlemen:

     This opinion is furnished in connection with the registration on Form S-3
(the "Registration Statement") pursuant to Rule 462(b) of the Securities Act of
1933, as amended (the "Securities Act"), of the issuance of up to 909,830 shares
(the "Redemption Shares") of common stock, par value $.01 per share ("Common
Stock"), of Boston Properties Inc. (the "Company") that may be issued by the
Company if and to the extent that common units of limited partnership interest
in Boston Properties Limited Partnership, a Delaware limited partnership (the
"Operating Partnership"), issued in connection with the acquisition of 875 Third
Avenue pursuant to an agreement dated November 21, 1997 (the "Redemption Units")
are presented to the Operating Partnership for redemption and the Company
exercises its right under the partnership agreement of the Operating Partnership
to acquire such Redemption Units in exchange for shares of Common Stock.

     In connection with rendering this opinion, we have examined the Amended and
Restated Certificate of Incorporation and Amended and Restated Bylaws of the
Company, each as amended to date; such records of the corporate proceedings of
the Company as we deemed material; and such other certificates, receipts,
records and documents as we considered necessary for the purposes of this
opinion.  In our examination, we have assumed the genuineness of all signatures,
the legal capacity of natural persons, the authenticity of all documents
submitted to us as certified, photostatic or facsimile copies, the authenticity
of the originals of such copies and the authenticity of telephonic confirmations
of public officials and others.  As to facts material to our opinion, we have
relied upon certificates or telephonic confirmations of public officials and
certificates, documents, statements and other information of the Company or
representatives or officers thereof.


Boston Properties, Inc.
June 30, 2000
Page 2

     We are attorneys admitted to practice in The Commonwealth of Massachusetts.
We express no opinion concerning the laws of any jurisdictions other than the
laws of the United States of America, the laws of The Commonwealth of
Massachusetts, and the Delaware General Corporation Law (which includes
applicable provisions of the Delaware Constitution and reported judicial
decisions interpreting the Delaware General Corporation Law and the Delaware
Constitution).

     Based upon the foregoing, we are of the opinion that, when the Redemption
Shares have been issued in exchange for Redemption Units tendered to the
Operating Partnership for redemption as contemplated by the limited partnership
agreement of the Operating Partnership, such Redemption Shares will be validly
issued, fully paid and nonassessable.

     The foregoing assumes that all requisite steps were taken to comply with
the requirements of the Securities Act and applicable requirements of state laws
regulating the offer and sale of securities.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to us with respect to this opinion
under the heading "Legal Matters" in the Prospectus which is a part of such
Registration Statement.  In giving such consent, we do not thereby admit that we
are in the category of persons whose consent is required under Section 7 of the
Act.

                                    Very truly yours,

                                    /s/ Goodwin, Procter & Hoar LLP

                                    GOODWIN, PROCTER & HOAR LLP