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
     1666 K STREET, N.W.                                   565 FIFTH AVENUE
   WASHINGTON, D.C. 20006                              NEW YORK, NEW YORK 10017
       (202) 775-8190                                       (212) 486-8200
    FAX NO. 202-293-2275                                 FAX NO. 212-758-2151






                                                              March 28, 2002



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,  2001 (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 the  Form  10-K,  and 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 and the by-laws of the Company,  each as
amended and restated;  and (ii) the sections in the Form 10-K captioned "Federal
Income  Tax  Considerations"  and  "ERISA  Plans,  Keogh  Plans  and  Individual
Retirement Accounts."

         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

Senior Housing Properties Trust
March 28, 2002
Page 2


"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 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.

         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  transactions  described  in the  Form  10-K (or the
documents  incorporated  therein by reference) have been consummated in a manner
that is  inconsistent  with the  manner  contemplated  therein,  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 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 the 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 the ERISA Laws.

         This opinion is intended solely for the benefit and use of the Company,
and is not to be used,  released,  quoted, or relied upon by anyone else for any
purpose  (other than as required by law) without our prior written  consent.  We
hereby  consent  to filing of a copy of this  opinion  as an exhibit to the Form
10-K, which is incorporated by reference in the Company's Registration Statement
on Form S-3 (File No.  333-76588)  under the  Securities Act of 1933, as amended
(the  "Act"),  and to the  references  to our  firm in the  Form  10-K  and such
Registration Statements. 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