EXHIBIT 8.1



                                             October 3, 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 October 3, 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; (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"; (iv) the Form S-1 filed by Five Star Quality Care, Inc., a Maryland
corporation




Senior Housing Properties Trust
October 3, 2001
Page 2


wholly owned by the Company, on September 21, 2001 (the "Form S-1") including
the section therein captioned "Federal Income Tax Considerations"; and (v) the
Company's Current Report on Form 8-K filed on October 1, 2001 (the "Form 8-K")
including the section therein captioned "Supplementary Federal Income Tax
Considerations".

         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", as supplemented by the section in the Form 8-K captioned
"Supplementary Federal Income Tax Considerations" and by 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 and the 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, if the transactions described in the Form S-1 and the Form 8-K
are consummated in a manner that is inconsistent with the manner contemplated
therein, 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
section in the Form 8-K captioned "Supplementary Federal Income Tax
Considerations" and by the section of 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.




Senior Housing Properties Trust
October 3, 2001
Page 3


         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.

         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,


                                              SULLIVAN & WORCESTER LLP