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





                                                              April 2, 2001


Senior Housing Properties Trust
400 Centre Street
Newton, Massachusetts  02458

Ladies and Gentlemen:

         In connection  with the filing by Senior  Housing  Properties  Trust, a
Maryland real estate  investment trust (the "Company"),  of its Annual Report on
Form 10-K for the year ended  December  31,  2000 (the "Form  10-K"),  under the
Securities  Exchange Act of 1934, as amended (the "Exchange Act"), the following
opinion  is  furnished  to you to be filed  with  the  Securities  and  Exchange
Commission (the "SEC") as Exhibit 8.1 to the Form 10-K.

         We have  acted  as  counsel  for the  Company  in  connection  with the
preparation  of its  Form  10-K,  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 opinions hereinafter set forth.  Specifically,
and without limiting the generality of the foregoing,  we have reviewed: (i) the
declaration  of trust  and the  by-laws  of the  Company,  each as  amended  and
restated;  and (ii) the sections in the Company's Form 10-K  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.

         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

Senior Housing Properties Trust
April 2, 2001
Page 2


change.  In preparing  the  discussions  with respect to Tax Laws and ERISA Laws
matters  in  the  sections  of the  Form  10-K  captioned  "Federal  Income  Tax
Considerations"  and  "ERISA  Plans,  Keogh  Plans  and  Individual   Retirement
Accounts," 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 Form 10-K captioned  "Federal Income Tax  Considerations"  and "ERISA Plans,
Keogh Plans and Individual  Retirement  Accounts," 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 Form 10-K and to the reference of our firm therein.  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