SC 13D/A

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                 SCHEDULE 13D/A
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
             TO RULE 13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT
                                TO RULE 13d-2(a)
                               (Amendment No. 3)*

                         SENIOR HOUSING PROPERTIES TRUST
                                (Name of Issuer)

              COMMON SHARES OF BENEFICIAL INTEREST, $.01 PAR VALUE
                         (Title of Class of Securities)

                                   81721M 10 9
                                 (CUSIP Number)

                                 John A. Mannix
                              HRPT Properties Trust
                                400 Centre Street
                                Newton, MA 02458
                                 (617) 332-3990
       (Name, Address and Telephone Number of Person Authorized to Receive
                          Notices and Communications)

                               September 28, 2001
             (Date of Event which Requires Filing of this Statement)


If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  that is the subject of this  Schedule  13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
/ /.

Note:  Schedules  filed in paper format shall include a signed original and five
copies of the  schedule,  including  all  exhibits.  See Rule 13d-7(b) for other
parties to whom copies are to be sent.

                         (Continued on following pages)

                               (Page 1 of 8 Pages)

-------------------------

* The remainder of this cover page shall be filled out for a reporting  person's
initial filing on this form with respect to the subject class of securities, and
for  any  subsequent   amendment   containing   information  which  would  alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the  Securities  Exchange  Act of
1934 ("Act") or otherwise  subject to the liabilities of that section of the Act
but  shall be  subject  to all other  provisions  of the Act  (however,  see the
Notes).








1     NAMES OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)


      HRPT Properties Trust
      I.R.S. ID No. 04-6558834

2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A  GROUP*    (a) / /
                                                            (b) / /


3     SEC USE ONLY




4     SOURCE OF FUNDS*


      WC

5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) OR 2(e)  / /


6     CITIZENSHIP OR PLACE OF ORGANIZATION


      Maryland

                          7         SOLE VOTING POWER
       NUMBER OF
         SHARES
      BENEFICIALLY                  12,809,238
        OWNED BY
          EACH            8         SHARED VOTING POWER
       REPORTING
         PERSON
          WITH
                          9         SOLE DISPOSITIVE POWER


                                    12,809,238

                          10        SHARED DISPOSITIVE POWER



11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON


      12,936,898

12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* / /


13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)


      29.79%

14    TYPE OF REPORTING PERSON*


      00

                *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                      -2-


1     NAMES OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)


      REIT Management & Research LLC

2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*            (a) / /
                                                                   (b) / /

3     SEC USE ONLY


4     SOURCE OF FUNDS*


      OO

5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) OR 2(e)   / /


6     CITIZENSHIP OR PLACE OF ORGANIZATION


      Delaware

                          7         SOLE VOTING POWER
       NUMBER OF
         SHARES
      BENEFICIALLY        8         SHARED VOTING POWER
        OWNED BY
          EACH
       REPORTING          9         SOLE DISPOSITIVE POWER
         PERSON
          WITH
                          10        SHARED DISPOSITIVE POWER



11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON


      12,954,002

12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* / /


13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)


      29.83

14    TYPE OF REPORTING PERSON*


      OO
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                      -3-


1     NAMES OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)


      REIT Management & Research Trust  I.R.S. ID No. 04-3402206

2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*       (a) / /
                                                              (b) / /


3     SEC USE ONLY


4     SOURCE OF FUNDS*


      OO

5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS
      2(d) OR 2(e)   / /


6     CITIZENSHIP OR PLACE OF ORGANIZATION


      Massachusetts

                          7         SOLE VOTING POWER
       NUMBER OF
         SHARES
      BENEFICIALLY        8         SHARED VOTING POWER
        OWNED BY
          EACH
       REPORTING          9         SOLE DISPOSITIVE POWER
         PERSON
          WITH
                          10        SHARED DISPOSITIVE POWER


11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON


      12,954,002

12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES* / /


13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)


      29.83%

14    TYPE OF REPORTING PERSON*


      OO
                *SEE INSTRUCTIONS BEFORE FILLING OUT!

                                      -4-





         This Amendment No. 3 to the original  Schedule 13D filed  September 29,
1999, by HRPT  Properties  Trust and REIT  Management & Research,  Inc. is being
filed to reflect a  decrease  in the  reported  percentage  ownership  of Senior
Housing   Properties   Trust  as  described   below  and  update  certain  other
information. This Amendment No. 3 shall also be an initial Schedule 13D filed by
REIT Management & Research Trust.

Item 1. Security and Issuer.

         The class of equity  securities to which this statement  relates is the
Common Shares of Beneficial Interest, par value $0.01 (the "Shares"),  of Senior
Housing Properties Trust, a Maryland real estate investment Trust ("SNH"),  with
its  principal   executive  offices  located  at  400  Centre  Street,   Newton,
Massachusetts 02458.

Item 2. Identity and Background.

         The persons filing this statement are HRPT Properties Trust, a Maryland
real estate investment trust ("HRP"), REIT Management & Research LLC, a Delaware
limited  liability  company  ("RMR"),  and REIT  Management & Research  Trust, a
Massachusetts  business trust ("RMR Trust").  Pursuant to an Agreement of Merger
and Plan of  Reorganization  dated  September  28,  2001  (the  "Merger"),  REIT
Management & Research, Inc., a Delaware corporation ("RMR, Inc.") and previously
a  reporting  person in this  Schedule  13D,  merged  with and into RMR, a newly
formed Delaware limited liability company that is wholly owned by RMR Trust. The
ownership of RMR Trust is the same as the  ownership of RMR,  Inc.,  immediately
prior to the Merger.  RMR succeeded to all of the assets of RMR, Inc.  including
all benefits and obligations of RMR, Inc. under the Advisory  Agreement  between
RMR, Inc. and SNH.

         HRP's  principal  business  is to operate as a real  estate  investment
trust.  The  principal  office of HRP is located at 400 Centre  Street,  Newton,
Massachusetts 02458. The trustees of HRP are Patrick F. Donelan,  Rev. Justinian
Manning, C.P., Frederick N. Zeytoonjian,  Barry M. Portnoy and Gerard M. Martin.
The executive officers of HRP are John A. Mannix,  President and Chief Operating
Officer,  John C. Popeo,  Treasurer,  Chief  Financial  Officer  and  Secretary,
Jennifer B. Clark,  Senior Vice  President and Assistant  Secretary and David M.
Lepore, Senior Vice President.

         RMR's principal  business is providing advisory services to real estate
investment trusts such as SNH and others. The principal office of RMR is located
at 400 Centre  Street,  Newton,  Massachusetts  02458.  The directors of RMR are
David J. Hegarty, Gerard M. Martin, and Barry M. Portnoy. The executive officers
of RMR are David J. Hegarty,  President and Secretary, John G. Murray, Executive
Vice  President,  Evrett W.  Benton,  Vice  President,  Jennifer B. Clark,  Vice
President and Assistant  Secretary,  David M. Lepore,  Vice  President,  John A.
Mannix,  Vice  President,  Thomas M.  O'Brien,  Vice  President,  John C. Popeo,
Treasurer,  John R.  Hoadley,  Vice  President  and Bruce J. Mackey,  Jr.,  Vice
President. The sole member and manager of RMR is RMR Trust.

         RMR Trust's  principal  business is to act as the member and manager of
RMR. The principal office of RMR Trust is located at 400 Centre Street,  Newton,
Massachusetts  02458. The trustees of RMR Trust are David J. Hegarty,  Gerard M.
Martin and Barry M. Portnoy.  The trustees and  executive  officers of RMR Trust
are the same as the  directors  and  executive  officers of RMR. Each of Messrs.
Martin and Portnoy own 50% of the outstanding capital stock of RMR Trust.

                                      -5-


         Each of the individuals  listed above (i) except for Mr. Donelan,  is a
United  Stated  citizen,  (ii)  except for Mr.  Donelan,  Rev.  Manning  and Mr.
Zeytoonjian,  has a business address at 400 Centre Street, Newton, Massachusetts
02458 and (iii) except for Mr. Donelan,  Rev.  Manning,  and Mr.  Zeytoonjian is
principally employed by RMR, in the capacities specified above. Mr. Hegarty also
serves as President,  Chief Operating Officer,  and Secretary of SNH and John R.
Hoadley  also  serves as  Treasurer  and Chief  Financial  Officer  of SNH.  The
principal office of SNH is located at 400 Centre Street,  Newton,  Massachusetts
02458.  Mr.  Donelan is a British  citizen and is Chairman  and Chief  Executive
Officer of  eSecLending  and has a business  address at Sion Hall,  56  Victoria
Embankment,  London, United Kingdom. Rev. Manning is the pastor of St. Gabriel's
parish at 139 Washington Street, Brighton,  Massachusetts 02135. Mr. Zeytoonjian
is Chairman and Chief Executive  Officer of Turf Products  Corporation and has a
business address at 157 Moody Road, Enfield, Connecticut 06083.

         Neither HRP, RMR, RMR Trust nor any of the individuals  specified above
has,  during  the last five  years,  been  convicted  in a  criminal  proceeding
(excluding  traffic  violations or similar  misdemeanors),  or been party to any
civil proceeding  which resulted in a judgment,  decree or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.

Item 5. Interest in securities of the issuer.

         (a) On October 7, 2001 and October 12, 2001, SNH issued an aggregate of
14,047,000  additional Shares in an underwritten public offering.  HRP continues
to hold  12,809,238  Shares,  which as a  result  of SNH's  offering  of  Shares
represent 29.50% of the issued and outstanding Shares.

         In addition,  the trustees and executive officers of HRP own SNH Shares
as follows:  Mr.  Martin,  through a corporation of which Mr. Martin is the sole
stockholder,  61,204  Shares;  Mr.  Portnoy,  through a corporation of which Mr.
Portnoy is the sole stockholder, 61,204 Shares; and other trustees and executive
officers of HRP, 5,252 Shares in the aggregate. In addition, Messrs. Portnoy and
Martin, as Managing Trustees of HRP, may be deemed to have beneficial  ownership
of the  12,809,238  Shares  held by HRP;  however,  Messrs.  Portnoy  and Martin
disclaim  beneficial  ownership of HRP's 12,809,238  Shares.  The Shares held by
HRP,  when  aggregated  with such  additional  Shares held by the  trustees  and
executive officers of HRP, aggregate  12,936,898 Shares,  which represent 29.79%
of the issued and outstanding Shares. The Shares held by Mr. Martin, Mr. Portnoy
and the  other  trustees  and  executive  officers  of HRP are  reported  herein
pursuant to the  provisions  of Items 2 and 5 of  Schedule  13D.  HRP,  however,
expressly  disclaims any beneficial  ownership of the Shares held by Mr. Martin,
Mr. Portnoy and the other trustees and executive officers of HRP.

         RMR, as HRP's advisor, and RMR Trust, as the sole member and manager of
RMR, may under applicable regulatory definitions,  be deemed to beneficially own
HRP's 12,809,238  Shares.  RMR and RMR Trust,  however,  expressly  disclaim any
beneficial ownership of HRP's 12,809,238 Shares.

                                      -6-


         In addition, the trustees,  directors and executive officers of RMR and
RMR Trust own SNH Shares as follows, in part as noted above: Mr. Martin, through
a corporation of which Mr. Martin is the sole  stockholder,  61,204 Shares;  Mr.
Portnoy,  through a corporation  of which Mr.  Portnoy is the sole  stockholder,
61,204 Shares;  Mr. Hegarty,  8,440 Shares;  and other executive officers of RMR
Trust,  13,916  Shares in the  aggregate.  The Shares  held by HRP (which may be
deemed to be beneficially owned by RMR and RMR Trust), when aggregated with such
additional Shares held by the trustees,  directors and executive officers of RMR
Trust,  aggregate  12,954,002  Shares,  which represent 29.83% of the issued and
outstanding Shares. The Shares held by Mr. Martin, Mr. Portnoy,  Mr. Hegarty and
the other  executive  officers of RMR and RMR Trust are reported herein pursuant
to the provisions of Items 2 and 5 of Schedule 13D. RMR and RMR Trust,  however,
expressly  disclaims any beneficial  ownership of the Shares held by Mr. Martin,
Mr. Portnoy, Mr. Hegarty and the other executive officers of RMR Trust.

         (b) HRP has sole power to vote or dispose of its 12,809,238  Shares. To
HRP's knowledge, each of the trustees,  directors and executive officers of HRP,
RMR and RMR Trust  described  above  has sole  power to vote or  dispose  of the
Shares he or she beneficially owns.

         (c) No  transactions in Shares have been effected during the past sixty
days by HRP, RMR, RMR Trust or the trustees, directors and executive officers of
HRP, RMR and RMR Trust described above.

         (d) No other  person is known to have the right to receive or the power
to direct the receipt of  distributions  from,  or the proceeds from the sale of
securities covered by this statement.


Item 7. Material to be Filed as Exhibits.

         The following documents are filed as exhibits to this statement:

         99.1.    Joint Filing  Agreement,  dated as of October 23, 2001, by and
                  among HRP, RMR and RMR Trust.


                                      -7-




                                    SIGNATURE


         After reasonable  inquiry and to the best of my knowledge and belief, I
certify that the information  set forth in this statement is true,  complete and
correct.

October 23, 2001                      HRPT PROPERTIES TRUST


                                      By: /s/ John Popeo
                                          Name: John Popeo
                                          Title:  Treasurer and Chief Financial
                                                   Officer



                                      REIT MANAGEMENT & RESEARCH LLC


                                      By: /s/ Jennifer B. Clark
                                          Name: Jennifer B. Clark
                                          Title:  Vice President and
                                                   Assistant Secretary



                                      REIT MANAGEMENT & RESEARCH TRUST


                                      By: /s/ Thomas M. O'Brien
                                          Name: Thomas M. O'Brien
                                          Title:  Vice President

EX-99.1

                                                                    EXHIBIT 99.1

                                    AGREEMENT

         Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934,
the undersigned hereby agree that only one statement  containing the information
required  by  Schedule  13D (or any  amendment  thereof)  need be filed on their
behalf with  respect to the  beneficial  ownership of any equity  securities  of
Senior  Housing  Properties  Trust,  a Maryland  real  estate  investment  trust
("SNH"), or any subsequent  acquisitions or dispositions of equity securities of
SNH by the undersigned.

October 23, 2001                      HRPT PROPERTIES TRUST



                                      By: /s/ John Popeo
                                      Name: John Popeo
                                      Title: Treasurer and Chief Financial
                                              Officer



                                      REIT MANAGEMENT & RESEARCH LLC



                                      By: /s/ Jennifer B. Clark
                                          Name: Jennifer B. Clark
                                          Title:  Vice President and
                                                   Assistant Secretary

                                      REIT MANAGEMENT & RESEARCH TRUST


                                      By: /s/ Thomas M. O'Brien
                                          Name: Thomas M. O'Brien
                                          Title:  Vice President