Exhibit 8.1

                            SULLIVAN & WORCESTER LLP
                             One Post Office Square
                           Boston, Massachusetts 02109




                                                March 11, 1998





Health and Retirement Properties Trust
400 Centre Street
Newton, Massachusetts 02158

Ladies and Gentlemen:

         In  connection  with the  filing by Health  and  Retirement  Properties
Trust, a Maryland real estate  investment trust (the  "Company"),  of its Annual
Report on Form 10-K for the year ended  December  31,  1997 (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 opinion  hereinafter set forth.  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 of the Company;
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 the officers of the Company.
We have not  independently  verified such  information;  nothing has come to our
attention,  however,  which would lead us to believe that we are not entitled to
rely on 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,





Health and Retirement Properties Trust
March 11, 1998
Page 2


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 the 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  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 to 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 Securities Act of 1933,
as  amended,  or  under  the  rules  and  regulations  of  the  SEC  promulgated
thereunder.

                                           Very truly yours,


                                           /s/ Sullivan & Worcester LLP

                                           SULLIVAN & WORCESTER LLP