Exhibit 8.1


                              SULLIVAN & WORCESTER LLP
                               ONE POST OFFICE SQUARE
                             BOSTON, MASSACHUSETTS 02109
                                   (617) 338-2800
                                FAX NO. 617-338-2880
     IN WASHINGTON, D.C.                                   IN NEW YORK CITY
1025 CONNECTICUT AVENUE, N.W.                              767 THIRD AVENUE
   WASHINGTON, D.C. 20036                              NEW YORK, NEW YORK 10017
       (202) 775-8190                                       (212) 486-8200
    FAX NO. 202-293-2275                                 FAX NO. 212-758-2151






                                           September 28, 2000




HRPT Properties Trust
400 Centre Street
Newton, Massachusetts  02458

Ladies and Gentlemen:

         In  connection  with  the  registration  by HRPT  Properties  Trust,  a
Maryland real estate  investment  trust (the  "Company"),  of $20,000,000 of its
8.625% Senior Notes due 2010,  the  following  opinion is furnished to you to be
filed with the Securities and Exchange  Commission (the "SEC") as Exhibit 8.1 to
the  Company's  Current  Report on Form 8-K, to be filed  within one week of the
date  hereof,  under  the  Securities  Exchange  Act of 1934,  as  amended  (the
"Exchange Act").

         We have  acted  as  counsel  for the  Company  in  connection  with its
Registration  Statement  on Form  S-3,  File No.  333-56051  (the  "Registration
Statement"),  under the Securities  Act of 1933, as amended (the "Act"),  and we
have  examined  originals or copies,  certified or otherwise  identified  to our
satisfaction,  of corporate records, certificates and statements of officers and
accountants of the Company and of public officials,  and such other documents as
we have  considered  relevant  and  necessary  in order to furnish  the  opinion
hereinafter set forth. Specifically,  and without limiting the generality of the
foregoing,  we have reviewed: (i) the Company's declaration of trust, as amended
and restated,  and the by-laws of the Company as amended and restated;  (ii) the
prospectus supplement dated September 28, 2000 (the "Prospectus  Supplement") to
the final  prospectus  dated June 15, 1998 (as  supplemented  by the  Prospectus
Supplement,  the "Prospectus") which forms a part of the Registration Statement;
and (iii) the sections in the  Company's  Form 10-K for the year ended  December
31, 1999 (the "Annual Report") captioned "Federal Income Tax Considerations" and
"ERISA Plans, Keogh Plans and Individual  Retirement  Accounts." With respect to
all  questions  of fact on which such  opinions  are based,  we have assumed the
accuracy and completeness of and have relied on the information set forth in the
Form  10-K  and in the  documents  incorporated  therein  by  reference,  and on
representations made to us by officers of the Company. We have not independently
verified such information.

HRPT Properties Trust
September 28, 2000
Page 2


         The opinion set forth below is based upon the Internal  Revenue Code of
1986,  as  amended,  the  Treasury  Regulations  issued  thereunder,   published
administrative  interpretations  thereof,  and judicial  decisions  with respect
thereto, all as of the date hereof (collectively,  the "Tax Laws"), and upon the
Employee  Retirement Income Security Act of 1974, as amended,  the Department of
Labor regulations issued thereunder,  published  administrative  interpretations
thereof,  and judicial decisions with respect thereto, all as of the date hereof
(collectively, the "ERISA Laws"). No assurance can be given that the Tax Laws or
the ERISA Laws will not change. In preparing the discussions with respect to Tax
Laws and ERISA Laws  matters in the  sections  of the  Annual  Report  captioned
"Federal Income Tax Considerations" and "ERISA Plans, Keogh Plans and Individual
Retirement  Accounts," and in the section of the Prospectus Supplement captioned
"Material Federal Income Tax  Considerations,"  we have made certain assumptions
and  expressed  certain  conditions  and  qualifications  therein,  all of which
assumptions, conditions and qualifications are incorporated herein by reference.

         Based upon and subject to the foregoing, we are of the opinion that the
discussions  with  respect to Tax Laws and ERISA Laws matters in the sections of
the Annual  Report  captioned  "Federal  Income Tax  Considerations"  and "ERISA
Plans, Keogh Plans and Individual  Retirement  Accounts," as supplemented by the
discussion in the Prospectus  Supplement  captioned "Material Federal Income Tax
Considerations,"  in all material respects are accurate and fairly summarize the
Tax Laws issues and ERISA Laws issues addressed therein, and hereby confirm that
the opinions of counsel  referred to in said sections  represent our opinions on
the subject matter thereof.

         We hereby consent to the  incorporation of this opinion by reference as
an exhibit to the Registration Statement and to the reference to our firm in the
Prospectus,  and to the  incorporation  of  this  opinion  by  reference  in the
Company's  Registration  Statement.  In giving such  consent,  we do not thereby
admit that we come  within the  category  of persons  whose  consent is required
under  Section  7 of the Act or  under  the  rules  and  regulations  of the SEC
promulgated thereunder.

                                               Very truly yours,

                                               /s/ SULLIVAN & WORCESTER LLP
                                               SULLIVAN & WORCESTER LLP