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






                                                              June 27, 2001




Senior Housing Properties Trust
400 Centre Street
Newton, Massachusetts  02458

Ladies and Gentlemen:

         In connection with the registration by Senior Housing Properties Trust,
a Maryland real estate investment trust (the "Company"), of its common shares of
beneficial interest,  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.  333-60392  (the  "Registration
Statement"),  under the Securities Act of 1933, as amended (the "Act").  We have
reviewed  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.  In doing so, we have  assumed  the  genuineness  of all
signatures,  the legal  capacity of natural  persons,  the  authenticity  of all
documents submitted to us as originals,  the conformity to original documents of
all  documents  submitted  to us as  certified or  photostatic  copies,  and the
authenticity  of the  originals  of such  documents.  Specifically,  and without
limiting the generality of the foregoing,  we have reviewed: (i) the declaration
of trust, as amended and restated,  and the by-laws, as amended and restated, of
the Company; (ii) the prospectus supplement dated June 28, 2001 (the "Prospectus
Supplement") to the final  prospectus dated May 21, 2001 (as supplemented by the
Prospectus Supplement,  the "Prospectus") which forms a part of the Registration
Statement; and (iii) the Company's Annual Report on Form 10-K for the year ended
December 31, 2000 filed under the Exchange Act (the "Annual Report"),  including
the sections therein captioned  "Federal Income Tax  Considerations"  and "ERISA
Plans, Keogh Plans and Individual Retirement Accounts."


Senior Housing Properties Trust
June 27, 2001
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, "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
"Federal Income Tax and ERISA  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.
With  respect to all  questions  of fact on which our opinion is based,  we have
assumed the initial and continuing truth,  accuracy and completeness of: (i) the
information set forth in the Annual Report, the Prospectus, and in the documents
incorporated  therein  by  reference;  and  (ii)  representations  made to us by
officers of the Company or contained in the Annual Report or Prospectus, in each
such instance  without regard to  qualifications  such as "to the best knowledge
of" or "in the belief of."

         We have relied upon,  but not  independently  verified,  the  foregoing
assumptions.  If any of the foregoing  assumptions  are inaccurate or incomplete
for any reason,  or if the issuance of the common shares of beneficial  interest
is consummated in a manner that is  inconsistent  with the manner in which it is
described in the  Prospectus,  our opinion as  expressed  below may be adversely
affected and may not be relied upon.

         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 "Federal Income Tax and ERISA
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.

         Our  opinion  above is  limited  to the  matters  specifically  covered
hereby, and we have not been asked to address, nor have we addressed,  any other
matters or any other  transactions.  Further,  we disclaim  any  undertaking  to
advise you of any  subsequent  changes of the  matters  stated,  represented  or
assumed herein or any subsequent changes in the Tax Laws or ERISA Laws.


Senior Housing Properties Trust
June 27, 2001
Page 3


         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.  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