Exhibit 1.0

                         SENIOR HOUSING PROPERTIES TRUST

                    13,000,000 Shares of Beneficial Interest

                             UNDERWRITING AGREEMENT


October 3, 2001



                             UNDERWRITING AGREEMENT

                                                                October 3, 2001

UBS Warburg LLC
Merrill Lynch, Pierce, Fenner & Smith
        Incorporated
A.G. Edwards & Sons, Inc.
Cantor Fitzgerald & Co.
First Union Securities, Inc.
Legg Mason Wood Walker, Incorporated
Tucker Anthony Incorporated

c/o UBS Warburg LLC
299 Park Avenue
New York, New York  10171-0026

Ladies and Gentlemen:

         Senior Housing Properties Trust, a real estate investment trust
organized under the laws of the State of Maryland (the "COMPANY"), proposes to
issue and sell to the underwriters named in SCHEDULE A annexed hereto (the
"UNDERWRITERS") an aggregate of 13,000,000 common shares (the "FIRM SHARES") of
beneficial interest, $.01 par value (the "COMMON SHARES"), of the Company. In
addition, solely for the purpose of covering over-allotments, the Company
proposes to grant to the Underwriters the option to purchase from the Company up
to an additional 1,950,000 Common Shares (the "ADDITIONAL SHARES"). The Firm
Shares and the Additional Shares are hereinafter collectively sometimes referred
to as the "SHARES." The Shares are described in the Prospectus which is referred
to below.

         The Company has prepared and filed with the Securities and Exchange
Commission (the "COMMISSION") in accordance with the provisions of the
Securities Act of 1933, as amended, and the rules and regulations of the
Commission thereunder (collectively, the "ACT"), a registration statement (file
number 333-60392) on Form S-3 under the Act (the "REGISTRATION STATEMENT"),
including a prospectus relating to, among other things, common shares of
beneficial interest, preferred shares of beneficial interest, depository shares,
guarantees, debt securities and warrants for such securities of the Company, and
such amendments to such registration statement as may have been required prior
to the date hereof have been similarly prepared and have been filed with the
Commission. Such registration statement, as so amended, and any post-effective
amendments thereto, have been declared by the Commission to be effective under
the Act. Such registration statement, as amended at the date of this Agreement,
meets the requirements set forth in Rule 415(a)(1)(x) under the Act and complies
in all other material respects with said Rule. The Company will next file with
the Commission pursuant to Rule 424(b) under the Act a final prospectus
supplement to the basic prospectus included in such

                                       2


registration statement, as so amended, describing the Shares and the offering
thereof, in such form as has been provided to or discussed with, and approved,
by the Underwriters.

         The term "REGISTRATION STATEMENT" as used in this Agreement means the
registration statement, as amended at the time it became effective, as
supplemented or amended prior to the execution of this Agreement, including (i)
all financial schedules and exhibits thereto and (ii) all documents incorporated
by reference or deemed to be incorporated by reference therein. If it is
contemplated, at the time this Agreement is executed, that a post-effective
amendment to the registration statement will be filed and must be declared
effective before the offering of the Shares may commence, the term "Registration
Statement" as used in this Agreement means the registration statement as amended
by said post-effective amendment. If an abbreviated registration statement is
prepared and filed with the Commission in accordance with Rule 462(b) under the
Act (an "ABBREVIATED REGISTRATION STATEMENT"), the term "Registration Statement"
includes the Abbreviated Registration Statement. The term "BASIC PROSPECTUS" as
used in this Agreement means the base prospectus dated May 21, 2001, as filed
with the Commission pursuant to Rule 424(b) included in the Registration
Statement. The term "PREPRICING PROSPECTUS" as used in this Agreement means the
preliminary form of the Prospectus Supplement (as defined herein) subject to
completion, if any, used in connection with the offering of the Shares. The term
"PROSPECTUS SUPPLEMENT" as used in this Agreement means any final prospectus
supplement specifically relating to the Shares, in the form filed with, or
transmitted for filing to, the Commission pursuant to Rule 424 under the Act.
The term "PROSPECTUS" as used in this Agreement means the Basic Prospectus
together with the Prospectus Supplement, except that if such Basic Prospectus is
amended or supplemented on or prior to the date on which the Prospectus
Supplement was first filed pursuant to Rule 424, the term "PROSPECTUS" shall
refer to the Basic Prospectus as so amended or supplemented and as supplemented
by the Prospectus Supplement. Any reference in this Agreement to the
registration statement, the Registration Statement, the Basic Prospectus, any
Prepricing Prospectus, any Prospectus Supplement or the Prospectus shall be
deemed to refer to and include the documents incorporated by reference therein
pursuant to Item 12 of Form S-3 under the Act, as of the date of the
registration statement, the Registration Statement, the Basic Prospectus, such
Prepricing Prospectus, such Prospectus Supplement or the Prospectus, as the case
may be, and any reference to any amendment or supplement to the registration
statement, the Registration Statement, the Basic Prospectus, any Prepricing
Prospectus, any Prospectus Supplement or the Prospectus shall be deemed to refer
to and include any documents filed after such date under the Securities Exchange
Act of 1934, as amended (the "EXCHANGE ACT"), which, upon filing, are
incorporated by reference therein, as required by paragraph (b) of Item 12 of
Form S-3. As used herein, the term "INCORPORATED DOCUMENTS" means the documents
which are incorporated by reference in the registration statement, the
Registration Statement, the Basic Prospectus, any Prepricing Prospectus, any
Prospectus Supplement, the Prospectus, or any amendment or supplement thereto.

         The Company and the Underwriters agree as follows:

         1. SALE AND PURCHASE. On the basis of the representations and
warranties herein and subject to the terms and conditions herein set forth, the
Company agrees to issue and sell to each Underwriter and, upon the basis of the
representations, warranties and agreements of the Company herein contained and
subject to all the terms and conditions set forth herein, each

                                       3


Underwriter agrees, severally and not jointly, to purchase from the Company, at
a purchase price of $12.24 per Share (the "PURCHASE PRICE PER SHARE"), the
number of Firm Shares set forth opposite the name of such Underwriter in
SCHEDULE A annexed hereto (or such number of Firm Shares increased as set forth
in Section 8 hereof).

         The Company is advised by you that the Underwriters intend (i) to make
a public offering of their respective portions of the Firm Shares as soon after
the date hereof as in your judgment is advisable and (ii) initially to offer the
Firm Shares upon the terms set forth in the Prospectus. You may from time to
time increase or decrease the public offering price after the initial public
offering to such extent as you may determine.

         In addition, the Company hereby grants to the several Underwriters the
option to purchase, and upon the basis of the representations, warranties and
agreements of the Company and subject to all the terms and conditions herein set
forth, the Underwriters shall have the right to purchase, severally and not
jointly, from the Company, ratably in accordance with the number of Firm Shares
to be purchased by each of them (subject to such adjustment as you shall
determine to avoid fractional shares), all or a portion of the Additional Shares
as may be necessary to cover over-allotments made in connection with the
offering of the Firm Shares, at the same purchase price per share to be paid by
the Underwriters to the Company for the Firm Shares. This option may be
exercised by you on behalf of the several Underwriters at any time (but not more
than once) on or before the thirtieth day following October 3, 2001, by written
notice to the Company. Such notice shall set forth the aggregate number of
Additional Shares as to which the option is being exercised, and the date and
time when the Additional Shares are to be delivered (such date and time being
herein referred to as the "ADDITIONAL TIME OF PURCHASE"); PROVIDED, HOWEVER,
that the additional time of purchase shall not be earlier than the time of
purchase (as defined below) nor earlier than the second business day1 after the
date on which the option shall have been exercised nor later than the tenth
business day after the date on which the option shall have been exercised. The
number of Additional Shares to be sold to each Underwriter shall be the number
which bears the same proportion to the aggregate number of Additional Shares
being purchased as the number of Firm Shares set forth opposite the name of such
Underwriter on SCHEDULE A hereto bears to the total number of Firm Shares
(subject, in each case, to such adjustment as you may determine to eliminate
fractional shares).

         2. PAYMENT AND DELIVERY. Payment of the purchase price for the Firm
Shares shall be made to the Company by Federal Funds wire transfer, against
delivery of the certificates for the Firm Shares to you through the facilities
of the Depository Trust Company ("DTC") for the respective accounts of the
Underwriters. Such payment and delivery shall be made at 10:00 A.M., New York
City time, on October 9, 2001 (unless another time shall be agreed to by you or
unless postponed in accordance with the provisions of Section 8 hereof). The
time at which such payment and delivery are actually made is hereinafter
sometimes called the "TIME OF PURCHASE." Certificates for the Firm Shares shall
be delivered to you in definitive form in such names and in

-----------------------------------
1  As used herein "BUSINESS DAY" shall mean a day on which the New York Stock
   Exchange is open for trading.

                                       4


such denominations as you shall specify no later than the second business day
preceding the time of purchase. For the purpose of expediting the checking of
the certificates for the Firm Shares by you, the Company agrees to make such
certificates available to you for such purpose at least one full business day
preceding the time of purchase.

         Payment of the purchase price for the Additional Shares shall be made
at the additional time of purchase in the same manner and at the same office as
the payment for the Firm Shares. Certificates for the Additional Shares shall be
delivered to you in definitive form in such names and in such denominations as
you shall specify no later than the second business day preceding the additional
time of purchase. For the purpose of expediting the checking of the certificates
for the Additional Shares by you, the Company agrees to make such certificates
available to you for such purpose at least one full business day preceding the
additional time of purchase.

         3. REPRESENTATIONS AND WARRANTIES OF THE COMPANY. The Company
represents and warrants to each of the Underwriters that:

         (a) No order preventing or suspending the use of the Basic Prospectus,
    any Prepricing Prospectus, the Prospectus Supplement or the Prospectus is in
    effect and no proceedings for such purpose are pending or, to the knowledge
    of the Company, threatened by the Commission or the securities authority of
    any state or other jurisdiction. The Registration Statement has become
    effective under the Act; no stop order suspending the effectiveness of the
    Registration Statement is in effect, and no proceedings for such purpose are
    pending before or, to the knowledge of the Company, threatened by the
    Commission or the securities authority of any state or other jurisdiction.

         (b) (i) The Company is eligible to use Form S-3 and the offering of the
    Shares complies with the requirements of Rule 415, (ii) each part of the
    Registration Statement, when such part became effective, and also any
    Abbreviated Registration Statement when it shall become effective, complied
    in all material respects with applicable requirements of the Act and the
    Exchange Act, (iii) each part of the Registration Statement, when such part
    became effective, did not contain and each such part, as may be amended or
    supplemented, if applicable, will not contain any untrue statement of a
    material fact or omit to state a material fact required to be stated therein
    or necessary to make the statements therein not misleading, (iv) the
    Registration Statement, any Abbreviated Registration Statement, the Basic
    Prospectus, any Prepricing Prospectus, the Prospectus Supplement and the
    Prospectus comply and, as may be amended or supplemented, if applicable,
    will comply in all material respects with the Act and the Exchange Act and
    (v) the Prospectus does not contain and, as may be amended or supplemented,
    if applicable, will not contain any untrue statement of a material fact or
    omit to state a material fact necessary to make the statements therein, in
    the light of the circumstances under which they were made, not misleading,
    except that the representations and warranties set forth in this paragraph
    (b) do not apply to statements or omissions in the Registration Statement,
    the Basic Prospectus, any Prepricing Prospectus, the Prospectus Supplement
    or the Prospectus based upon information relating to any Underwriter
    furnished to the Company by such Underwriter through you expressly for use
    therein.

                                       5


         (c) The Incorporated Documents, when they were filed with the
    Commission, conformed in all material respects to the requirements of the
    Exchange Act, and none of such documents, when they were filed with the
    Commission, contained an untrue statement of a material fact or omitted to
    state a material fact necessary to make the statements therein not
    misleading; and any further documents so filed and incorporated by reference
    in (a) the Registration Statement, when such documents are filed with the
    Commission, will conform in all material respects to the requirements of the
    Exchange Act, as applicable, and will not contain an untrue statement of a
    material fact or omit to state a material fact necessary to make the
    statements therein not misleading, and (b) the Prospectus, when such
    documents are filed with the Commission, will conform in all material
    respects to the requirements of the Exchange Act, as applicable, and will
    not contain an untrue statement of a material fact or omit to state a
    material fact necessary to make the statements therein, in the light of the
    circumstances in which they were made, not misleading.

         (d) As of the date of this Agreement, the Company has and will have an
    authorized capitalization as set forth in the Prospectus; all of the issued
    and outstanding Common Shares of the Company have been duly and validly
    authorized and issued and are fully paid and non-assessable, have been
    issued in compliance with all federal and state securities laws and were not
    issued in violation of any preemptive or similar right.

         (e) The Company has been duly formed and is existing as a real estate
    investment trust in good standing under the laws of the State of Maryland,
    with trust power to own, lease and operate its properties and conduct its
    business as described in the Registration Statement.

         (f) The Company is duly qualified to do business as a foreign
    corporation and is in good standing in each jurisdiction in which the
    ownership or leasing of its properties or the conduct of its business
    requires such qualification, except where the failure to so qualify in any
    such jurisdiction would not individually or in the aggregate have a material
    adverse effect on the business, prospects, properties, condition (financial
    or otherwise) or results of operations of the Company and the Subsidiaries
    (as defined herein), taken as a whole (a "MATERIAL ADVERSE EFFECT").

         (g) The Company has no subsidiaries other than those identified in
    SCHEDULE B hereto (collectively, the "SUBSIDIARIES"). Other than the
    Subsidiaries, the Company does not own, directly or indirectly, any shares
    of stock or any other equity or long-term debt of any other corporation or
    have any direct or indirect equity interest or ownership of long-term debt
    in any firm, partnership, joint venture, limited liability company,
    association or other entity except for the Company's ownership of 1,000,000
    common shares of HRPT Properties Trust and 100 common shares of Marriott
    International, Inc. Each Subsidiary has been duly incorporated or formed and
    is validly existing as a corporation or other entity, as the case may be, in
    good standing under the laws of the jurisdiction of its incorporation or
    organization, with the requisite corporate, trust, partnership or other
    power to acquire and own, lease and operate its properties and to conduct
    its business, as described in the Registration Statement and the Prospectus;
    and each Subsidiary is duly qualified and in good standing to do business in
    each

                                       6


    jurisdiction in which the nature of its business or the ownership or
    leasing of the property requires such qualification, except where the
    failure to be so qualified would not have a Material Adverse Effect.

         (h) This Agreement has been duly authorized, executed and delivered by
    the Company.

         (i) The shares of beneficial interest of the Company, including the
    Shares, conform in all material respects to the description thereof included
    or incorporated by reference in the Registration Statement and the
    Prospectus. The certificates evidencing the Shares are in due and proper
    form and conform in all material respects to the requirements of the
    Maryland REIT Law.

         (j) The Shares have been duly and validly authorized and, when issued
    and delivered against payment therefor as provided herein, will be duly and
    validly issued, fully paid and non-assessable and, except as described in
    the Registration Statement, free of any preemptive or similar rights.

         (k) Neither the Company nor any of the Subsidiaries is in breach or
    violation of, or in default under (and no event has occurred which with
    notice, lapse of time, or both would result in any breach or violation of,
    or constitute a default under), its Declaration of Trust, charter or by-laws
    or other organizational documents or in the performance or observance of any
    obligation, agreement, covenant or condition contained in any indenture,
    mortgage, deed of trust, loan agreement or other agreement or instrument to
    which the Company or any Subsidiary is subject or by which any of them or
    any of their properties is bound or affected, the effect of which would,
    individually or in the aggregate, have a Material Adverse Effect.

         (l) Except as would not individually or in the aggregate have a
    Material Adverse Effect, the issuance by the Company of the Shares, the
    compliance by the Company with all of the provisions of this Agreement, the
    execution, delivery and performance by the Company of this Agreement, and
    the consummation of the transactions contemplated herein will not conflict
    with or result in a breach or violation of any of the terms or provisions
    of, or constitute a default under, any indenture, mortgage, deed of trust,
    loan agreement or other agreement or instrument to which the Company or any
    Subsidiary is a party or by which the Company or any Subsidiary is bound or
    to which any of the property or assets of the Company or any Subsidiary is
    subject. In addition, such action will not result in any violation of the
    provisions of the Declaration of Trust or the bylaws of the Company or any
    of the Company's other organizational documents or applicable laws or any
    order, rule or regulation of any court or governmental agency or body having
    jurisdiction over the Company or any of its or its Subsidiaries' properties.

         (m) No approval, authorization, consent or order of or filing with any
    federal, state or local or foreign governmental or regulatory commission,
    board, body, authority or agency is required in connection with the issuance
    and sale of the Shares or the consummation by the Company of the transaction
    as contemplated hereby other than

                                       7


    registration of the Shares under the Act and any necessary qualification
    under the securities or blue sky laws of the various jurisdictions in which
    the Shares are being offered by the Underwriters.

         (n) Except as set forth in the Registration Statement and the
    Prospectus: (i) no person has the right, contractual or otherwise, to cause
    the Company to issue to it, or register pursuant to the Act, any shares of
    beneficial interest or other equity interests; and (ii) no person has
    preemptive rights, co-sale rights, rights of first refusal or other rights
    to purchase any Common Shares. No person has the right, contractual or
    otherwise, to cause the Company to register under the Act any shares of
    beneficial interest or other equity interests as a result of the filing or
    effectiveness of the Registration Statement or the sale of Shares
    contemplated thereby, except for such rights as have been complied with or
    waived.

         (o) Ernst & Young LLP, whose report on the consolidated financial
    statements of the Company and the Subsidiaries was filed with the Commission
    as part of the Company's Annual Report on Form 10-K for the fiscal year
    ended December 31, 2000 and is incorporated by reference in the Registration
    Statement and Prospectus, are independent public accountants as required by
    the Act.

         (p) KPMG LLP, whose report on the financial statements with respect to
    42 nursing home facilities was filed with the Commission as part of the
    Company's Current Report on Form 8-K/A and is incorporated by reference in
    the Registration Statement and Prospectus, are independent public
    accountants as required by the Act.

         (q) Arthur Andersen LLP, whose report on the financial statements with
    respect to 31 facilities ("Crestline Facilities") to be acquired by the
    Company pursuant to a Stock Purchase Agreement, dated August 9, 2001, among
    the Company, SNH/CSL Properties Trust, Crestline Capital Corporation and CSL
    Group, Inc. was filed with the Commission as part of the Company's Current
    Report on Form 8-K, dated September 21, 2001 (the "September 21, 2001 8-K"),
    and is incorporated by reference in the Registration Statement and
    Prospectus, are independent public accountants as required by the Act.

         (r) All legal or governmental proceedings, contracts, leases or
    documents of a character required to be described in the Registration
    Statement or the Prospectus or any Incorporated Document, and all documents
    required to be filed as an exhibit to the Registration Statement or any
    Incorporated Document, have been so described or filed or will be filed
    prior to the time of purchase as required.

         (s) Except as otherwise set forth in the Prospectus, there are no legal
    or governmental proceedings pending to which the Company or any of the
    Subsidiaries is a party or of which any of the Company's or any of the
    Subsidiaries' properties or assets or, to the knowledge of the Company, any
    of the properties of the Company and the Subsidiaries that is the subject,
    the result of which would, individually or in the aggregate, have a Material
    Adverse Effect, and, to the Company's knowledge, no such proceedings are
    threatened or contemplated, except as disclosed in the Prospectus, the

                                       8


    result of which would, individually or in the aggregate, have a Material
    Adverse Effect. To the Company's knowledge, there are no legal or
    governmental proceedings pending to which any lessee, sublessee or operator
    of any property of the Company or any Subsidiary or portion thereof is a
    party, the result of which would, individually or in the aggregate, have a
    Material Adverse Effect, and no such proceedings are being threatened or
    contemplated, except as disclosed in the Prospectus and the result of which
    would, individually or in the aggregate, have a Material Adverse Effect.
    Neither the Company nor any of the Subsidiaries has received from any
    governmental authority notice of any violation of any local, state or
    federal law, rule or regulation including without limitation any such law,
    rule or regulation applicable to the health care industry ("HEALTH CARE
    LAWS") or relating to human health or safety or the environment or any
    hazardous or toxic substances or wastes, pollutants or contaminants
    ("ENVIRONMENTAL LAWS"), except as disclosed in the Prospectus, the result of
    which would, individually or in the aggregate, have a Material Adverse
    Effect, and to the Company's knowledge, there is no such violation, or any
    occurrence or circumstance that would give rise to a claim under or pursuant
    to any local, state or federal law, rule or regulation (including without
    limitation any Health Care Laws or Environmental Laws), which would,
    individually or in the aggregate, have a Material Adverse Effect. To the
    Company's knowledge, there is no violation of any local, state or federal
    law, rule or regulation (including without limitation Health Care Laws and
    Environmental Laws) by any person from whom the Company or any of the
    Subsidiaries acquired any of its properties (a "SELLER"), or any lessee,
    sublessee or operator of any of their respective properties or any part
    thereof, the result of which would, individually or in the aggregate, have a
    Material Adverse Effect, and to the Company's knowledge, there is no such
    violation, or any occurrence or circumstance that would give rise to a claim
    under or pursuant to any local, state or federal law, rule or regulation
    (including without limitation any Health Care Laws or Environmental Laws),
    which would, individually or in the aggregate, have a Material Adverse
    Effect, except as disclosed in the Prospectus. Neither the Company nor any
    of the Subsidiaries has received from any governmental authority any written
    notice of any condemnation of or zoning change affecting the properties or
    any part thereof of the Company or any of the Subsidiaries that individually
    or in the aggregate would have a Material Adverse Effect and the Company
    does not know of any such condemnation or zoning change which is threatened
    and which if consummated individually or in the aggregate would have a
    Material Adverse Effect. Nothing has come to the Company's attention that
    any seller, lessee, sublessee or operator of any property of the Company or
    any of the Subsidiaries, or portion thereof has, received from any
    governmental authority any written notice of any condemnation of or zoning
    change affecting the Properties or any part thereof of the Company or any of
    the Subsidiaries that individually or in the aggregate would have a Material
    Adverse Effect.

         (t) Each of the Company and the Subsidiaries have good and marketable
    title in fee simple or ground leases to the properties disclosed in the
    Prospectus as being owned by them (the "PROPERTIES"), free and clear of all
    liens, encumbrances, claims, mortgages, deeds of trust, restrictions,
    security interests and defects ("PROPERTY ENCUMBRANCES"), except for: (x)
    the leasehold interests of lessees in the Company's and the Subsidiaries'
    properties held under lease (the "LEASES") and (y) any other Property
    Encumbrances that would not, individually or in the aggregate, have a
    Material Adverse

                                       9


    Effect. All Property Encumbrances on or affecting the properties of the
    Company or any of the Subsidiaries which are required to be disclosed in the
    Prospectus are disclosed therein. Each of the Leases pertaining to the
    properties of the Company or any of the Subsidiaries has been duly
    authorized by the Company or one of the Subsidiaries, as applicable, and is
    a valid and binding agreement of the Company or one of the Subsidiaries, as
    applicable, and, to the Company's knowledge, each other party thereto,
    enforceable in accordance with its terms, except as enforcement thereof may
    be limited by bankruptcy, insolvency, moratorium, fraudulent conveyance or
    other similar laws affecting the enforcement of creditors' rights generally
    and by general equitable principles. To the Company's knowledge, no lessee
    of any portion of any of the properties of the Company or any of the
    Subsidiaries is in default under its respective lease and there is no event
    which, but for the passage of time or the giving of notice or both, would
    constitute a default under any such lease, except such defaults that would
    not, individually or in the aggregate, have a Material Adverse Effect.

         (u) The Company and each of the Subsidiaries and, to the Company's
    knowledge, each of the operators, lessees or sublessees of any property or
    portion thereof of the Company or any of the Subsidiaries have such permits,
    licenses, approvals, certificates, franchises and authorizations of
    governmental or regulatory authorities ("PERMITS"), including, without
    limitation, under any Health Care Laws or Environmental Laws, as are
    necessary in the case of each such party to acquire and own, lease or
    operate its properties and to conduct its business, all as described in the
    Prospectus, except where the failure to obtain such permits would not
    individually or in the aggregate have a Material Adverse Effect; except as
    described in the Prospectus, the Company and each of the Subsidiaries and,
    to the Company's knowledge, each of the lessees, sublessees or operators of
    any property or portion thereof of the Company or any of the Subsidiaries
    have fulfilled and performed all of their obligations with respect to such
    permits and, except as disclosed in the Prospectus, no event has occurred
    which allows, or after notice or lapse of time would allow, revocation or
    termination thereof or result in any other impairment of the rights of the
    holder of any such permit, except where the failure to fulfill or perform,
    or the resulting termination or impairment, would not, individually or in
    the aggregate, have a Material Adverse Effect; and, except as described in
    the Prospectus, such permits contain no restrictions that are burdensome to
    the Company and the Subsidiaries, taken as a whole and that would,
    individually or in the aggregate, have a Material Adverse Effect.

         (v) The financial statements, together with the related schedules and
    notes, forming a part of the Registration Statement and the Prospectus
    present fairly the consolidated financial position of the Company and the
    Subsidiaries as of the dates indicated and the consolidated results of
    operations and cash flows of the Company and the Subsidiaries for the
    periods specified. Such financial statements have been prepared in
    conformity with generally accepted accounting principles applied on a
    consistent basis during the periods involved. The pro forma financial
    statements and other pro forma financial data included or incorporated by
    reference in the Registration Statement and the Prospectus comply as to form
    in all material respects with the applicable accounting requirements of
    Regulation S-X of the Act, and the pro forma adjustments have been properly
    applied to the historical amounts in the compilation of those statements.
    The

                                       10


    other financial and statistical data set forth in the Registration Statement
    and the Prospectus are accurately presented and prepared on a basis
    consistent with such financial statements and books and records of the
    Company. There are no financial statements (historical or pro forma) that
    are required to be included in the Registration Statement and the Prospectus
    that are not included as required.

         (w) Subsequent to the respective dates as of which information is given
    in the Registration Statement and the Prospectus, there has not been (i) any
    material adverse change, or any prospective material adverse change, in the
    business, properties, condition (financial or otherwise) or results of
    operations of the Company and the Subsidiaries taken as a whole, (ii) any
    transaction which is material to the Company or the Subsidiaries, (iii) any
    obligation, direct or contingent, which is material to the Company and the
    Subsidiaries taken as a whole, incurred by the Company or the Subsidiaries,
    (iv) any material change in the shares of beneficial interest or material
    increase in the outstanding indebtedness of the Company or the Subsidiaries,
    (v) any dividend or distribution of any kind declared, paid or made on the
    shares of beneficial interest of the Company other than (A) regular
    quarterly dividends, declared, paid or made or a dividend distribution of
    any kind on any class of its shares of beneficial interest (other than
    dividends or distributions from wholly-owned subsidiaries of the Company)
    and (B) the issuance of common shares of beneficial interest to the trustees
    and officers pursuant to the Company's Incentive Share Award Plan, or (vi)
    to the Company's knowledge, any material adverse change, or any prospective
    material adverse change, in the business, properties, condition (financial
    or otherwise) or results of operations of the business of the Crestline
    Facilities, as described in the September 21, 2001 8-K, taken as a whole.
    None of the Company nor the Subsidiaries has any material contingent
    obligation which is not disclosed in the Registration Statement.

         (x) Each of the Company and the Subsidiaries are insured by insurers of
    recognized financial responsibility against such losses and risks and in
    such amount as are customary in the business in which they are engaged,
    except as described in the Prospectus. Except as would not, individually or
    in the aggregate, have a Material Adverse Effect, all policies of insurance
    insuring the Company and the Subsidiaries or any of their businesses,
    assets, employees, officers, directors and trustees are in full force and
    effect, and the Company and the Subsidiaries are in compliance with the
    terms of such policies in all material respects. Except as would not,
    individually or in the aggregate, have a Material Adverse Effect, there are
    no claims by the Company or any of the Subsidiaries under any such policy or
    instrument as to which any insurance company is denying liability or
    defending under a reservation of rights clause.

         (y) Except as disclosed in the Registration Statement, neither the
    Company nor any of the Subsidiaries has either sent or received any
    communication regarding termination of, or intent not to renew, any of the
    contracts or agreements referred to or described in, or filed as an exhibit
    to, the Registration Statement or any Incorporated Document, and no such
    termination or non-renewal has been threatened by the Company or any of the
    Subsidiaries or any other party to any such contract or agreement.

                                       11


         (z)  Neither the Company nor any of the Subsidiaries or any of their
    respective affiliates has taken, directly or indirectly, any action designed
    to or which has constituted or which might reasonably be expected to cause
    or result, under the Exchange Act or otherwise, in stabilization or
    manipulation of the price of any security of the Company to facilitate the
    sale or resale of the Shares.

         (aa) The Company and the Subsidiaries have not sustained since the date
    of the latest audited financial statements included in the Prospectus any
    loss or interference with their businesses from fire, explosion, flood or
    other calamity, whether or not covered by insurance, or from any labor
    dispute or court or governmental action, order or decree, otherwise than as
    disclosed in the Prospectus or other than any loss or interference, which
    would individually or in the aggregate not have a Material Adverse Effect.

         (bb) The Company and the Subsidiaries maintain a system of internal
    accounting controls sufficient to provide reasonable assurances that (i)
    transactions are executed in accordance with management's general or
    specific authorization; (ii) transactions are recorded as necessary to
    permit preparation of financial statements in conformity with generally
    accepted accounting principles and to maintain accountability for assets;
    (iii) access to assets is permitted only in accordance with management's
    general or specific authorization; and (iv) the recorded accountability for
    assets is compared with existing assets at reasonable intervals and
    appropriate action is taken with respect to any differences.

         (cc) The Company and the Subsidiaries have filed all federal, state,
    local and foreign tax returns and tax forms required to be filed. Such
    returns and forms are complete and correct in all material respects, and all
    taxes shown by such returns or otherwise assessed that are due or payable
    have been paid, except such taxes as are being contested in good faith and
    as to which adequate reserves have been provided. All payroll withholdings
    required to be made by the Company and the Subsidiaries with respect to
    employees have been made except where the failure to fulfill or perform,
    would not, individually or in the aggregate, have a Material Adverse Effect.
    The charges, accruals and reserves on the books of the Company and the
    Subsidiaries in respect of any tax liability for any year not finally
    determined are adequate to meet any assessments or reassessments for
    additional taxes. There have been no tax deficiencies asserted and, to the
    Company's knowledge, no tax deficiency might be reasonably asserted or
    threatened against the Company and/or the Subsidiaries that would
    individually or in the aggregate have a Material Adverse Effect.

         (dd) The outstanding Common Shares are, and the Shares will be, subject
    to official notice of issuance and evidence of satisfactory distribution,
    listed on the New York Stock Exchange (the "NYSE").

         (ee) The Company meets the requirements for qualification and taxation
    as a real estate investment trust ("REIT") under the Internal Revenue Code
    of 1986 (the "CODE").

                                       12


         (ff) The Company is not and, after giving effect to the offering and
    sale of the Shares, will not be an "investment company" or an entity
    "controlled" by an "investment company," as such terms are defined in the
    Investment Company Act of 1940, as amended (the "INVESTMENT COMPANY ACT").

         4. CERTAIN COVENANTS.

         (a) The Company hereby agrees:

             (i) to furnish such information as may be required and otherwise to
    cooperate in qualifying the Shares for offering and sale under the
    securities or blue sky laws of such states as you may designate and to
    maintain such qualifications in effect so long as required for the
    distribution of the Shares; PROVIDED that the Company shall not be required
    to qualify as a foreign corporation or to consent to the service of process
    under the laws of any such state (except service of process with respect to
    the offering and sale of the Shares); and to promptly advise you of the
    receipt by the Company of any notification with respect to the suspension of
    the qualification of the Shares for sale in any jurisdiction or the
    initiation or threatening of any proceeding for such purpose;

             (ii) to make available to the Underwriters in New York City as many
    copies of the Prospectus (or of the Prospectus as amended or supplemented if
    the Company shall have made any amendments or supplements thereto) as the
    Underwriters may reasonably request for the purposes contemplated by the
    Act; in case any Underwriter is required to deliver a prospectus beyond the
    nine-month period referred to in Section 10(a)(3) of the Act in connection
    with the sale of the Shares, the Company will prepare promptly upon request,
    but at its expense, such amendment or amendments to the Registration
    Statement and such prospectuses as may be necessary to permit compliance
    with the requirements of Section 10(a)(3) of the Act;

             (iii) to advise you promptly, confirming such advice in writing, of
    any request by the Commission for amendments or supplements to the
    Registration Statement or Prospectus or for additional information with
    respect thereto, or of notice of institution of proceedings for, or the
    entry of a stop order suspending the effectiveness of the Registration
    Statement and, if the Commission should enter a stop order suspending the
    effectiveness of the Registration Statement, to make every reasonable effort
    to obtain the lifting or removal of such order as soon as possible; to
    advise you promptly of any proposal to amend or supplement the Registration
    Statement or Prospectus, including by filing any documents that would be
    incorporated therein by reference and to file no such amendment or
    supplement to which you shall object in writing;

                                       13


             (iv) to file promptly all reports and any definitive proxy or
    information statement required to be filed by the Company with the
    Commission in order to comply with the Exchange Act subsequent to the date
    of the Prospectus and for so long as the delivery of a prospectus is
    required in connection with the offering or sale of the shares, and to
    promptly notify you of such filing;

             (v) if, at the time this Agreement is executed and delivered, it is
    necessary for the registration statement or a post-effective amendment
    thereto or any Abbreviated Registration Statement to be declared effective
    before the offering of the Shares may commence, the Company will endeavor to
    cause the registration statement or such post-effective amendment to become
    effective as soon as possible and will advise you promptly and, if requested
    by you, will confirm such advice in writing, when the registration statement
    or such post-effective amendment has become effective;

             (vi) to furnish to you and, upon request, to each of the other
    Underwriters for a period of three years from the date of this Agreement (i)
    copies of any reports or other communications which the Company shall send
    to its shareholders or shall from time to time publish or publicly
    disseminate, (ii) copies of all annual, quarterly and current reports filed
    with the Commission on Forms 10-K, 10-Q and 8-K, or such other similar form
    as may be designated by the Commission, (iii) copies of documents or reports
    filed with any national securities exchange on which any class of securities
    of the Company is listed, and (iv) such other information as you may
    reasonably request regarding the Company or the Subsidiaries, in each case
    as soon as such communications, documents or information becomes available;
    PROVIDED, HOWEVER, that in no case shall the Company be required to furnish
    materials pursuant to this paragraph which are filed and publicly accessible
    via EDGAR;

             (vii) to advise the Underwriters promptly of the happening of any
    event known to the Company within the time during which a Prospectus
    relating to the Shares is required to be delivered under the Act which, in
    the judgment of the Company, would require the making of any change in the
    Prospectus then being used, or in the information incorporated therein by
    reference, so that the Prospectus would not include an untrue statement of
    material fact or omit to state a material fact necessary to make the
    statements therein, in the light of the circumstances under which they are
    made, not misleading, and, during such time, to prepare and furnish, at the
    Company's expense, to the Underwriters promptly such amendments or
    supplements to such Prospectus as may be necessary to reflect any such
    change and to furnish you a copy of such proposed amendment or supplement
    before filing any such amendment or supplement with the Commission;

             (viii) to make generally available to its security holders, and to
    deliver to you, an earnings statement of the Company (which will satisfy the

                                       14


    provisions of Section 11(a) of the Act) covering a period of twelve months
    beginning after the effective date of the Registration Statement (as defined
    in Rule 158(c) of the Act) as soon as is reasonably practicable after the
    termination of such twelve-month period;

             (ix) to furnish to its shareholders as soon as practicable after
    the end of each fiscal year an annual report (including a balance sheet and
    statements of income, shareholders' equity and of cash flow of the Company)
    for such fiscal year, accompanied by a copy of the certificate or report
    thereon of nationally recognized independent certified public accountants;

             (x) to furnish to you one conformed copy of the Registration
    Statement, as initially filed with the Commission, and of all amendments
    thereto (including all exhibits thereto and documents incorporated by
    reference therein) and sufficient conformed copies of the foregoing (other
    than exhibits) for distribution of a copy to each of the other Underwriters;

             (xi) to furnish to you as early as practicable prior to the time of
    purchase and the additional time of purchase, as the case may be, but not
    later than two business days prior thereto, a copy of the latest available
    unaudited interim consolidated financial statements, if any, of the Company
    and the Subsidiaries which have been read by the Company's independent
    certified public accountants, as stated in their letter to be furnished
    pursuant to Section 6(d) hereof;

             (xii) to apply the net proceeds from the sale of the Shares in the
    manner set forth under the caption "Use of proceeds" in the Prospectus;

            (xiii) to pay all expenses, fees and taxes in connection with (i)
    the preparation and filing of the Registration Statement, each Preliminary
    Prospectus, the Prospectus, and any amendments or supplements thereto, and
    the printing and furnishing of copies of each thereof to the Underwriters
    and to dealers (including costs of mailing and shipment), (ii) the issuance,
    sale and delivery of the Shares by the Company, (iii) the word processing
    and/or printing of this Agreement, any Agreement Among Underwriters and any
    dealer agreements and the reproduction and/or printing and furnishing of
    copies of each thereof to the Underwriters and to dealers (including costs
    of mailing and shipment), (iv) the qualification of the Shares for offering
    and sale under state laws and the determination of their eligibility for
    investment under state law as aforesaid (including the legal fees and filing
    fees and other disbursements of counsel to the Underwriters) and the
    printing and furnishing of copies of any blue sky surveys or legal
    investment surveys to the Underwriters and to dealers and (v) the filing for
    review of the public offering of the Shares by the NASDR (including the
    legal fees and filing fees and other disbursements of counsel to the
    Underwriters with respect thereto), (vi) any listing of the Shares on any
    securities exchange and any registration

                                       15


    thereof under the Exchange Act, and (vii) the performance of the Company's
    other obligations under this Agreement;

             (xiv) to furnish to you, before filing with the Commission
    subsequent to the effective date of the Registration Statement and during
    the period referred to in paragraph (a)(vii) above, a copy of any document
    proposed to be filed pursuant to Section 13, 14 or 15(d) of the Exchange
    Act;

             (xv) not to sell, offer to sell, contract to sell, hypothecate,
    pledge, grant any option to sell or otherwise dispose of, directly or
    indirectly, any Common Shares or securities convertible into or exchangeable
    or exercisable for Common Shares or options, warrants or other rights to
    purchase Common Shares or any other shares of the Company that are
    substantially similar to Common Shares or file a registration statement
    under the Act relating to the offer and sale of any Common Shares or
    securities convertible into or exchangeable or exercisable for Common Shares
    or options, warrants or other rights to purchase Common Shares or any other
    shares of the Company that are substantially similar to Common Shares for a
    period of ninety (90) days after the date hereof (the "LOCK-UP PERIOD"),
    without the prior written consent of UBS Warburg LLC, except for (i)
    issuances of Common Shares upon the exercise of outstanding options or
    warrants as disclosed in the Registration Statement and the Prospectus to
    persons who have entered into Lock-Up Agreements with the Underwriters, (ii)
    the issuance of employee stock options not exercisable during the Lock-up
    Period pursuant to stock option plans described in the Registration
    Statement and the Prospectus, (iii) issuances of Common Shares under the
    Company's Incentive Share Award Plan described in the Registration Statement
    and the Prospectus and (iv) issuances of Common Shares as partial or full
    payment for properties directly or indirectly acquired or to be acquired by
    the Company or its subsidiaries; PROVIDED that, the Company shall have
    conditioned such issuances of Common Shares upon agreement of the recipients
    to the restrictions of this paragraph;

             (xvi) to use its best efforts to cause the Shares to be listed on
    the NYSE; and

            (xvii) to use its best efforts to continue to qualify as a REIT
    under Sections 856 through 860 of the Code.

         5. REIMBURSEMENT OF UNDERWRITERS' EXPENSES. If the Shares are not
delivered for any reason other than the termination of this Agreement pursuant
to clause (ii), (iii) or (iv) of the second paragraph of Section 7 hereof or
pursuant to the last paragraph of Section 8 hereof or the default by one or more
of the Underwriters in its or their respective obligations hereunder, the
Company shall, in addition to paying the amounts described in Section 4 hereof,
reimburse the Underwriters for all of their out-of-pocket expenses, including
the reasonable fees and disbursements of their counsel.

                                       16


         6. CONDITIONS OF UNDERWRITERS' OBLIGATIONS. The several obligations of
the Underwriters hereunder are subject to the accuracy of the representations
and warranties on the part of the Company on the date hereof and at the time of
purchase (and the several obligations of the Underwriters at the additional time
of purchase are subject to the accuracy of the representations and warranties on
the part of the Company on the date hereof and at the time of purchase (unless
previously waived) and at the additional time of purchase, as the case may be),
the performance by the Company of its obligations hereunder and to the following
additional conditions precedent:

         (a) The Company shall furnish to you at the time of purchase and at the
    additional time of purchase, as the case may be, an opinion of Sullivan &
    Worcester LLP, counsel for the Company, addressed to the Underwriters, and
    dated the time of purchase or the additional time of purchase, as the case
    may be, with reproduced copies for each of the other Underwriters and in
    form satisfactory to Dewey Ballantine LLP, counsel for the Underwriters,
    stating that:

             (i) the Company has been duly formed, is existing as a real estate
         investment trust and is in good standing under the laws of the State of
         Maryland, with trust power to own, lease and operate its properties and
         conduct its business in all material respects as described in the
         Registration Statement and the Prospectus, to execute and deliver this
         Agreement and to issue, sell and deliver the Shares as herein
         contemplated;

             (ii) the Company is duly qualified to transact business and is in
         good standing in each other jurisdiction in which it owns or leases
         properties, or conducts any business, so as to require such
         qualification, other than those jurisdictions as to which the failure
         to be so qualified or in good standing could not, individually or in
         the aggregate, reasonably be expected to have a Material Adverse
         Effect;

             (iii) each Subsidiary of the Company identified in SCHEDULE C
         attached hereto (each a "MATERIAL SUBSIDIARY") is a corporation or
         other legal entity duly formed, existing and in good standing under the
         laws of its jurisdiction of organization, and is duly qualified as a
         foreign corporation or other legal entity and is in good standing in
         each jurisdiction in which such qualification is required by law, other
         than those jurisdictions as to which the failure to be so qualified or
         in good standing could not, individually or in the aggregate,
         reasonably be expected to have a Material Adverse Effect. Each Material
         Subsidiary has the corporate, trust, partnership or other power to own
         or hold under lease the properties it purports to own or hold under
         lease and to transact the business it transacts and proposes to
         transact. All of the issued and outstanding shares of beneficial
         ownership of, or other ownership interests in, of each Material
         Subsidiary has been duly authorized and validly issued, is fully paid
         and except as to Material Subsidiaries that are partnerships,
         non-assessable, and except for SPTMRT Properties Trust, is owned by the
         Company, directly or through subsidiaries, free and clear of any
         security interest, mortgage, pledge, lien or encumbrance;

                                       17


             (iv) this Agreement has been duly authorized, executed and
         delivered by the Company, and is a legal, valid and binding agreement
         of the Company, enforceable in accordance with its terms, except as
         enforcement of the same may be limited by bankruptcy, insolvency,
         moratorium, fraudulent conveyance or other similar laws affecting the
         enforcement of creditors' rights generally and by general equitable
         principles and except as to those provisions relating to indemnities
         for liabilities arising under the Act as to which no opinion need be
         expressed;

             (v) the Shares to be sold by the Company have been duly authorized
         and, when issued and delivered to and paid for by the Underwriters,
         will be validly issued, fully paid and non-assessable and are not
         subject to preemptive or, to the knowledge of such counsel, similar
         rights;

             (vi) the Company has authorized and outstanding shares of
         beneficial interest as set forth or incorporated by reference in the
         Registration Statement and the Prospectus; the outstanding shares of
         beneficial interest of the Company have been duly and validly
         authorized and issued and are fully paid, nonassessable and free of any
         preemptive rights, resale rights, rights of first refusal and similar
         rights under any contract, agreement or instrument to which the Company
         is a party described in or filed as an exhibit to the Registration
         Statement or otherwise known to such counsel;

             (vii) the Registration Statement and the Prospectus (except as to
         the financial statements and schedules and other financial and
         statistical data contained therein, as to which such counsel need
         express no opinion) comply as to form in all material respects with the
         requirements of the Act;

             (viii) the Registration Statement has become effective under the
         Act and, to such counsel's knowledge, no stop order proceedings with
         respect thereto are pending or threatened under the Act and any
         required filing of the Prospectus, and any supplement thereto pursuant
         to Rule 424 under the Act, has been made in the manner and within the
         time period required by such Rule 424;

             (ix) the execution, delivery and performance of this Agreement by
         the Company and the transactions contemplated hereby do not and will
         not conflict with, or result in any breach of, or constitute a
         violation under (nor constitute any event which with notice, lapse of
         time, or both, would result in any breach of, or constitute a default
         under) (A) any provisions of the Declaration of Trust, charter, by-laws
         or other organizational documents of the Company or any of the Material
         Subsidiaries, (B) any provision of any material agreement or other
         instrument to which the Company or any of the Material Subsidiaries is
         a party or by which their respective properties may be bound or
         affected, that is described in the Prospectus or filed as an exhibit to
         the Registration Statement or any Incorporated Document or is otherwise
         known to such counsel or (C) any federal, state, local or foreign law,

                                       18


         regulation or rule, or any decree, to which the Company or the Material
         Subsidiaries may be subject;

             (x) to such counsel's knowledge, there are no contracts, licenses,
         agreements, leases or documents of a character which are required to be
         filed as exhibits to the Registration Statement or to be described in
         the Prospectus which have not been so filed or described;

             (xi) to such counsel's knowledge, except as described in the
         Prospectus or as would not, individually or in the aggregate, have a
         Material Adverse Effect, there are no private or governmental actions,
         suits, claims, investigations or proceedings pending, threatened or
         contemplated to which the Company or any of the Subsidiaries or any of
         their officers is subject or of which any of their properties is
         subject, whether at law, in equity or before or by any federal, state,
         local or foreign governmental or regulatory commission, board, body,
         authority or agency;

             (xii) to such counsel's knowledge, no person has the right,
         pursuant to the terms of any contract, agreement or other instrument
         described in or filed as an exhibit to the Registration Statement or
         any Incorporated Document, to cause the Company to register under the
         Act any shares of beneficial interest or other equity interests as a
         result of the filing or effectiveness of the Registration Statement or
         the sale of the Shares as contemplated hereby, except for such rights
         as have been complied with or waived; and to the knowledge of such
         counsel, except as described in the Registration Statement and
         Prospectus, no person is entitled to registration rights with respect
         to shares of capital stock or other securities of the Company;

             (xiii) the Company is not, and after the offering and sale of the
         Shares, will not be, an "investment company," or an entity controlled
         by an "investment company," as such terms are defined in the Investment
         Company Act; and

             (xiv) to such counsel's knowledge the statements in (i) the
         Registration Statement and the Prospectus under the captions
         "Description of common shares", "Our tenants and property operations",
         and "Federal income tax and ERISA considerations"; (ii) in the
         Company's Annual Report on Form 10-K for the fiscal year ended December
         31, 2000 under the captions "Business--Financing Policies" (with
         respect to the first paragraph only), "Business--Regulation and
         Reimbursement", "Business--Government Regulations and Rate Setting" and
         "Federal Income Tax Considerations"; and (iii) in the September 21,
         2001 8-K under the caption "C. Supplementary Federal Income Tax
         Considerations" in each case insofar as such statements purport to
         summarize matters arising under Maryland, Massachusetts or New York law
         or the federal law of the United States, or provisions of documents

                                       19


         as to which the Company is a party specifically referred to therein,
         are accurate in all material respects.

         In addition, such counsel shall state that, in the opinion of such
counsel, and subject to the restrictions and limitations set forth in such
counsel's tax opinion filed as an exhibit to the Registration Statement, (a) the
Company has qualified to be taxed as a REIT under the Code for each of its
fiscal years and (b) the proposed method of operation described in the
Prospectus and as represented to such counsel by the Company will enable the
Company to continue to satisfy the requirements for such qualification for
subsequent fiscal years under the Code. Actual qualification as a REIT, however,
will depend upon the Company's continued ability to meet, and its meeting,
through actual annual operating results and distributions, the various
qualifying tests under the Code.

         Also, such counsel shall state that it has participated in conferences
with officers and other representatives of the Company, representatives of the
independent public accountants of the Company and representatives of the
Underwriters at which the contents of the Registration Statement and Prospectus
were discussed and, although such counsel is not passing upon and does not
assume responsibility for the accuracy, completeness or fairness of the
statements contained in the Registration Statement or Prospectus (except as and
to the extent stated in subparagraphs (vii) and (xiv) above), on the basis of
the foregoing nothing has come to the attention of such counsel that causes them
to believe that the Registration Statement or any amendment thereto at the time
such Registration Statement or amendment became effective contained an untrue
statement of a material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements therein not misleading, or
that the Prospectus or any supplement thereto at the date of the Prospectus
Supplement or such other supplement, and at all times up to and including the
time of purchase or additional time of purchase, as the case may be, contained
an untrue statement of a material fact or omitted to state a material fact
required to be stated therein or necessary to make the statements therein, in
light of the circumstances under which they were made, not misleading (it being
understood that such counsel need express no opinion with respect to the
financial statements and schedules and other financial and statistical data and
exhibits included or incorporated by reference in the Registration Statement or
Prospectus).

         In rendering their opinion as aforesaid, Sullivan & Worcester LLP may
rely upon an opinion, dated as of the time of purchase or the additional time of
purchase, as the case may be, of Ballard Spahr Andrews & Ingersoll, LLP as to
matters governed by Maryland law, provided that such reliance is expressly
authorized by such opinion and a copy of such opinion is delivered to the
Underwriters and is, in form and substance, satisfactory to the Underwriters and
counsel for the Underwriters. In addition, in rendering such opinion, such
counsel may state that their opinion as to laws of the State of Delaware is
limited to the Delaware General Corporation Law and that their opinion with
respect to the qualification of the Company and is Subsidiaries to do business
in jurisdictions other than their respective jurisdiction of organization is
based solely upon certificates to such effect issued by an appropriate official
of the applicable jurisdictions.

         (b) The Company shall furnish to you at the time of purchase and at the
    additional time of purchase, as the case may be, an opinion of Ballard Spahr
    Andrews & Ingersoll, LLP, special Maryland counsel of the Company, addressed
    to the Underwriters,

                                       20


    and dated the time of purchase or the additional time of purchase, as the
    case may be, with reproduced copies for each of the other Underwriters and
    in form satisfactory to Dewey Ballantine LLP, counsel for the Underwriters,
    stating that:

             (i) the Company has been duly formed, is existing as a real estate
         investment trust and is in good standing under the laws of the State of
         Maryland, with trust power to own, lease and operate its properties and
         conduct its business in all material respects as described in the
         Registration Statement and the Prospectus, to execute and deliver this
         Agreement and to issue, sell and deliver the shares as herein
         contemplated;

             (ii) each Subsidiary of the Company identified in SCHEDULE D
         attached hereto (each a "MARYLAND SUBSIDIARY") is a corporation or
         other legal entity duly formed, existing and in good standing under the
         laws of its jurisdiction of organization. Each Maryland Subsidiary has
         the trust power to own or hold under lease the properties it purports
         to own or hold under lease and to transact the business it transacts
         and proposes to transact. All of the issued and outstanding shares of
         beneficial interest of each Maryland Subsidiary have been duly
         authorized and validly issued, is fully paid and non-assessable and is
         owned by the Company, directly or through subsidiaries, and to such
         counsel's knowledge, except for SPTMRT Properties Trust, free and clear
         of any security interest, mortgage, pledge, lien, encumbrance, claim or
         equity;

             (iii) the execution, delivery and performance of this agreement by
         the Company and the transactions contemplated hereby and by the
         Registration Statement do not and will not conflict with, or result in
         any breach of, or constitute a default under (nor constitute any event
         which with notice, lapse of time, or both, would result in any breach
         of, or constitute a default under) (A) any provisions of the
         Declaration of Trust, charter or by-laws or other organizational
         documents of the Company or any of the Maryland Subsidiaries or (B) any
         local or state Maryland law or administrative regulation applicable to
         the Company and the Maryland Subsidiaries;

             (iv) the Company has authorized and outstanding shares of
         beneficial interest as set forth or incorporated by reference in the
         Registration Statement and the Prospectus; the outstanding shares of
         beneficial interest of the Company have been duly and validly
         authorized and issued by all necessary trust action and are fully paid,
         nonassessable and free of any preemptive rights, resale rights, rights
         of first refusal and similar rights under the Maryland REIT Law; the
         Shares being sold by the Company, when issued, will be free of any
         preemptive rights, resale rights, rights of first refusal and similar
         rights under the Maryland REIT Law; and the certificates for the Shares
         are in due and proper form and conform in all material respects to the
         requirements of the Maryland REIT Law;

                                       21


             (v) no approval, authorization, consent or order of or filing with
         any Maryland governmental or regulatory commission, board, body,
         authority or agency having jurisdiction over the Company is required in
         connection with the execution, delivery and performance of this
         Agreement, the issuance and sale of the Shares being delivered at the
         time of purchase and at the additional time of purchase, as the case
         may be, or and the consummation of the transactions contemplated hereby
         and by the Prospectus (In rendering the opinion expressed in this
         paragraph (v), such counsel need express no opinion concerning the
         securities laws of the State of Maryland.);

             (vi) to such counsel's knowledge the statements in (i) the
         Registration Statement and the Prospectus under the captions
         "Description of common shares" and "Description of certain provisions
         of Maryland law and of our declaration of trust and bylaws" and in each
         case insofar as such statements purport to summarize matters arising
         under Maryland law are accurate in all material respects;

             (vii) to such counsel's knowledge, neither the Company nor any of
         the Maryland Subsidiaries is in violation of its Declaration of Trust,
         charter or by-laws or other organizational documents or in violation of
         any local or state Maryland law or administrative regulation applicable
         to the Company and the Maryland Subsidiaries; and

             (viii) except as described in the Registration Statement and the
         Prospectus, all of the outstanding shares of capital stock of each of
         the Maryland Subsidiaries that is a REIT have been duly authorized and
         validly issued, are fully paid and non-assessable, are owned by the
         Company.

         (c) You shall have received at the time of purchase and at the
    additional time of purchase, as the case may be, an opinion of Dewey
    Ballantine LLP, counsel for the Underwriters, dated the time of purchase and
    the additional time of purchase, as the case may be, with respect to the
    issuance and sale of the Securities by the Company, the Registration
    Statement, the Prospectus and such other related matters as the Underwriters
    may require. In addition, Dewey Ballantine LLP may rely on the opinion of
    Ballard Spahr Andrews & Ingersoll, LLP as to all matters of Maryland law.

         (d) You shall have received from Ernst & Young LLP, a letter dated,
    respectively, the date of this Agreement and the time of purchase and the
    additional time of purchase, as the case may be, and addressed to the
    Underwriters (with reproduced copies for each of the Underwriters) in the
    forms approved by Dewey Ballantine LLP, counsel for the Underwriters.

         (e) You shall have received from KPMG LLP, a letter dated,
    respectively, the date of this Agreement and the time of purchase and
    addressed to the Underwriters (with reproduced copies for each of the
    Underwriters) in the forms approved by Dewey Ballantine LLP, counsel for the
    Underwriters.

                                       22


         (f) You shall have received from Arthur Andersen LLP, a letter dated,
    respectively, the date of this Agreement and the time of purchase and
    addressed to the Underwriters (with reproduced copies for each of the
    Underwriters) in the forms approved by Dewey Ballantine LLP, counsel for the
    Underwriters.

         (g) No amendment or supplement to the Registration Statement or
    Prospectus, including documents deemed to be incorporated by reference
    therein, shall have been to which you have objected in writing.

         (h) Prior to the time of purchase and the additional time of purchase,
    as the case may be, (i) no stop order with respect to the effectiveness of
    the Registration Statement shall have been issued under the Act or
    proceedings initiated under Section 8(d) or 8(e) of the Act; (ii) the
    Registration Statement and all amendments thereto, or modifications thereof,
    if any, shall not contain an untrue statement of a material fact or omit to
    state a material fact required to be stated therein or necessary to make the
    statements therein not misleading; and (iii) the Prospectus and all
    amendments or supplements thereto, or modifications thereof, if any, shall
    not contain an untrue statement of a material fact or omit to state a
    material fact required to be stated therein or necessary to make the
    statements therein, in the light of the circumstances under which they are
    made, not misleading.

         (i) Between the time of execution of this Agreement and the time of
    purchase and the additional time of purchase, as the case may be, (i) no
    material and unfavorable change, financial or otherwise (other than as
    referred to in the Registration Statement and Prospectus), in the business,
    prospects, properties, condition of the Company and the Subsidiaries taken
    as a whole shall occur or become known and (ii) no transaction which is
    material and unfavorable to the Company and the Subsidiaries taken as a
    whole shall have been entered into by the Company or any of the
    Subsidiaries.

         (j) Between the time of execution of this Agreement and the time of
    purchase or the additional time of purchase, as the case may be, there shall
    not have occurred any downgrading, nor shall any notice or announcement have
    been given or made of (i) any intended or potential downgrading or (ii) any
    review or possible change that does not indicate an improvement, in the
    rating accorded any securities of or guaranteed by the Company by any
    "nationally recognized statistical rating organization," as that term is
    defined in Rule 436(g)(2) under the Act.

         (k) You shall have received the agreement (a "LOCK-UP AGREEMENT") of
    each of Barry M. Portnoy, Gerard M. Martin, David J. Hegarty, John R.
    Hoadley and HRPT Properties Trust not to sell, offer to sell, contract to
    sell, hypothecate, grant any option to sell or otherwise dispose of,
    directly or indirectly, any Common Shares or securities convertible into or
    exchangeable for Common Shares or warrants or other rights to purchase
    Common Shares for a period of 90 days after the date of the Prospectus
    Supplement without the prior written consent of UBS Warburg LLC.

         (l) The Company will, at the time of purchase and the additional time
    of purchase, as the case may be, deliver to you a certificate of two of its
    executive officers

                                       23


    to the effect that the representations and warranties of the Company as set
    forth in this Agreement are true and correct as of such date, that the
    Company has performed such of its obligations under this Agreement as are to
    be performed at or before the time of purchase and the conditions set forth
    in paragraphs (g), (h) and (i) of this Section 6 have been met.

         (m) The Company will, at the time of purchase and the additional time
    of purchase, as the case may be, deliver to you a certificate signed by the
    President of the Company substantially in such form approved by you and
    counsel to the Underwriters, respecting the Company's compliance, both prior
    to and after giving effect to the transactions contemplated hereby, with the
    financial covenants set forth in the Company's credit agreement and certain
    other agreements and instruments respecting outstanding indebtedness of the
    Company and the Subsidiaries.

         (n) The Shares shall have been approved for listing on the New York
    Stock Exchange (the "NYSE").

         The Company shall have furnished to you such other documents and
certificates as to the accuracy and completeness of any statement in the
Registration Statement and the Prospectus as of the time of purchase or the
additional time of purchase, as the case may be, as you may reasonably request.

         7. EFFECTIVE DATE OF AGREEMENT; TERMINATION. This Agreement shall
become effective: (i) upon the execution and delivery hereof by the parties
hereto; or (ii) if, at the time this Agreement is executed and delivered, it is
necessary for the registration statement or a post-effective amendment thereto
or an Abbreviated Registration Statement to be declared or become effective
before the offering of the Shares may commence, when notification of the
effectiveness of the registration statement or such post-effective amendment has
been released by the Commission or such Abbreviated Registration Statement has,
pursuant to the provisions of Rule 462 under the Act, become effective. Until
such time as this Agreement shall have become effective, it may be terminated by
the Company, by notifying you, or by you, as Underwriters, by notifying the
Company.

         The obligations of the several Underwriters hereunder shall be subject
to termination in the absolute discretion of you or any group of Underwriters
(which may include you) which has agreed to purchase in the aggregate at least
50% of the Firm Shares (i) if, since the time of execution of this Agreement or
the respective dates as of which information is given in the Registration
Statement and Prospectus, (y) there has been any material adverse and
unfavorable change, financial or otherwise (other than as referred to in the
Registration Statement and Prospectus), in the business, prospects, properties,
condition (financial or otherwise) or results of operations of the Company and
the Subsidiaries taken as a whole, which would, in your judgment or in the
judgment of such group of Underwriters, make it impracticable to market the
Shares, or (z) there shall have occurred any downgrading, or any notice shall
have been given of (a) any intended or potential downgrading or (b) any review
or possible change that does not indicate an improvement, in the rating accorded
any securities of or guaranteed by the Company or any of the Subsidiaries by any
"nationally recognized statistical rating organization", as that term is defined
in Rule 436(g)(2) under the Act or (ii) if, at any time

                                       24


prior to the time of purchase or, with respect to the purchase of any Additional
Shares, the additional time of purchase, as the case may be, trading in
securities on the New York Stock Exchange ("NYSE"), the American Stock Exchange
or the Nasdaq Stock Market Inc. ("Nasdaq") shall have been suspended or
limitations or minimum prices shall have been established on the NYSE, the
American Stock Exchange or the Nasdaq or (iii) if, at any time prior to the time
of purchase or, with respect to the purchase of any Additional Shares, the
additional time of purchase, as the case may be, a banking moratorium shall have
been declared either by the United States or New York State authorities, or (iv)
if, at any time prior to the time of purchase or, with respect to the purchase
of any Additional Shares, the additional time of purchase, as the case may be,
the United States shall have declared war in accordance with its constitutional
processes or there shall have occurred any material outbreak or escalation of
hostilities or other national or international calamity or crisis of such
magnitude in its effect on the financial markets of the United States as, in
your judgment or in the judgment of such group of Underwriters, to make it
impracticable to market the Shares.

         If you or any group of Underwriters elects to terminate this Agreement
as provided in this Section 7, the Company and each other Underwriter shall be
notified promptly by letter, telegram or telecopy.

         If the sale to the Underwriters of the Shares, as contemplated by this
Agreement, is not carried out by the Underwriters for any reason permitted under
this Agreement or if such sale is not carried out because the Company shall be
unable to comply with any of the terms of this Agreement, the Company shall not
be under any obligation or liability under this Agreement (except to the extent
provided in Sections 4, 5 and 9 hereof), and the Underwriters shall be under no
obligation or liability to the Company under this Agreement (except to the
extent provided in Section 9 hereof) or to one another hereunder.

         8. INCREASE IN UNDERWRITERS' COMMITMENTS. Subject to Sections 6 and 7,
if any Underwriter shall default in its obligation to take up and pay for the
Firm Shares to be purchased by it hereunder (otherwise than for reasons
sufficient to justify the termination of this Agreement under the provisions of
Section 7 hereof) and if the number of Firm Shares which all Underwriters so
defaulting shall have agreed but failed to take up and pay for does not exceed
10% of the total aggregate number of Firm Shares, the non-defaulting
Underwriters shall take up and pay for (in addition to the Firm Shares they are
obligated to purchase pursuant to Section 1 hereof) the Firm Shares agreed to be
purchased by all such defaulting Underwriters, as hereinafter provided. Such
Firm Shares shall be taken up and paid for by such non-defaulting Underwriter or
Underwriters in such numbers as you may designate with the consent of each
Underwriter so designated or, in the event no such designation is made, such
Firm Shares shall be taken up and paid for by all non-defaulting Underwriters
pro rata in proportion to the aggregate number of Firm Shares set opposite the
names of such non-defaulting Underwriters in SCHEDULE A.

         If a new Underwriter or Underwriters are substituted by the
Underwriters or by the Company for a defaulting Underwriter or Underwriters in
accordance with the foregoing provision, the Company or you shall have the right
to postpone the time of purchase or the additional time of purchase, as the case
may be, for a period not exceeding five business days in order that any
necessary changes in the Prospectus and other documents may be effected.

                                       25


         The term Underwriter as used in this agreement shall refer to and
include any Underwriter substituted under this Section 8 with like effect as if
such substituted Underwriter had originally been named in SCHEDULE A.

         If the aggregate number of Shares which the defaulting Underwriter or
Underwriters agreed to purchase exceeds 10% of the total aggregate number of
Shares which all Underwriters agreed to purchase hereunder, and if neither the
non-defaulting Underwriters nor the Company shall make arrangements within the
five business day period stated above for the purchase of all the Shares which
the defaulting Underwriter or Underwriters agreed to purchase hereunder, this
Agreement shall be terminated without further act or deed and without any
liability on the part of the Company to any non-defaulting Underwriter and
without any liability on the part of any non-defaulting Underwriter to the
Company. Nothing in this paragraph, and no action taken hereunder, shall relieve
any defaulting Underwriter from liability in respect of any default of such
Underwriter under this Agreement.

         9. INDEMNITY AND CONTRIBUTION.

         (a) The Company agrees to indemnify, defend and hold harmless each
Underwriter, its partners, directors, officers, employees and agents and any
person who controls any Underwriter within the meaning of Section 15 of the Act
or Section 20 of the Exchange Act, and the successors and assigns of all of the
foregoing persons, from and against any loss, damage, expense, liability or
claim (including the reasonable cost of investigation) which, jointly or
severally, any such Underwriter or any such person may incur under the Act, the
Exchange Act, the common law or otherwise, insofar as such loss, damage,
expense, liability or claim arises out of or is based upon (i) any untrue
statement or alleged untrue statement of a material fact contained in the
Registration Statement, the Basic Prospectus, any Prepricing Prospectus, any
Prospectus Supplement or in the Prospectus (or in any of the foregoing as the
same may at any time be amended or supplemented), or arises out of or is based
upon any omission or alleged omission to state a material fact required to be
stated in the Registration Statement, the Basic Prospectus, any Prepricing
Prospectus, any Prospectus Supplement or the Prospectus (or in any of the
foregoing as the same may at any time be amended or supplemented) or necessary
to make the statements made therein not misleading, except insofar as any such
loss, damage, expense, liability or claim arises out of or is based upon any
untrue statement or alleged untrue statement of a material fact contained in and
in conformity with information furnished by or on behalf of any Underwriter
through you to the Company expressly for use with reference to such Underwriter
in the Registration Statement, the Basic Prospectus, any Prepricing Prospectus,
any Prospectus Supplement or the Prospectus (or in any of the foregoing as the
same may at any time be amended or supplemented) or arises out of or is based
upon any omission or alleged omission to state a material fact in connection
with such information required to be stated in the Registration Statement, the
Basic Prospectus, any Prepricing Prospectus, any Prospectus Supplement or the
Prospectus (or in any of the foregoing as the same may at any time be amended or
supplemented) or necessary to make such information not misleading or (ii) any
untrue statement or alleged untrue statement made by the Company in Section 3 of
this Agreement or the failure by the Company to perform when and as required any
agreement or covenant contained herein or (iii) any untrue statement or alleged
untrue statement of any material fact contained in any audio or visual materials
provided by the Company or based upon written information furnished by or, with
the approval of the Company, on behalf of the

                                       26


Company including, without limitation, slides, videos, films, tape recordings,
used in connection with the marketing of the Shares; PROVIDED, however, that,
solely with regard to clause (i), the foregoing indemnity agreement with respect
to any Basic Prospectus or Prepricing Prospectus shall not inure to the benefit
of any Underwriter from whom the person asserting such losses, claims, damages
or liabilities purchased Securities, or any person controlling the Underwriter,
if sufficient copies of the Prospectus were timely delivered to such Underwriter
pursuant to Section 4 hereof and a copy of the Prospectus (as then amended or
supplemented if the Company shall have furnished any amendments or supplements
thereto) was not given or sent to such person, if required by law to have been
delivered, at or prior to the written confirmation of the sale of the Securities
to such person, and if the Prospectus (as so amended or supplemented) would have
cured the defect giving rise to such losses, claims, damages or liabilities.

         If any action, suit or proceeding (together, a "PROCEEDING") is brought
against an Underwriter or any such person in respect of which indemnity may be
sought against the Company pursuant to the foregoing paragraph, such Underwriter
or such person shall promptly notify the Company in writing of the institution
of such Proceeding and the Company shall assume the defense of such Proceeding,
including the employment of counsel reasonably satisfactory to such indemnified
party and payment of all fees and expenses related thereto; PROVIDED, HOWEVER,
that the omission to so notify the Company shall not relieve the Company from
any liability which the Company may have to any Underwriter or any such person
or otherwise. Such Underwriter or such person shall have the right to employ its
or their own counsel in any such case, but the fees and expenses of such counsel
shall be at the expense of such Underwriter or of such person unless the
employment of such counsel shall have been authorized in writing by the Company
in connection with the defense of such Proceeding or the Company shall not have,
within a reasonable period of time in light of the circumstances, employed
counsel to have charge of the defense of such Proceeding or such indemnified
party or parties shall have reasonably concluded that there may be defenses
available to it or them which are different from, additional to or in conflict
with those available to the Company (in which case the Company shall not have
the right to direct the defense of such Proceeding on behalf of the indemnified
party or parties), in any of which events such fees and expenses shall be borne
by the Company and paid as incurred (it being understood, however, that the
Company shall not be liable for the expenses of more than one separate counsel
(in addition to any local counsel) in any one Proceeding or series of related
Proceedings in the same jurisdiction representing the indemnified parties who
are parties to such Proceeding). The Company shall not be liable for any
settlement of any such Proceeding effected without its prior written consent but
if settled with the prior written consent of the Company, the Company agrees to
indemnify and hold harmless any Underwriter and any such person from and against
any loss or liability by reason of such settlement. Notwithstanding the
foregoing sentence, if at any time an indemnified party shall have requested an
indemnifying party to reimburse the indemnified party for fees and expenses of
counsel as contemplated by the second sentence of this paragraph, then the
indemnifying party agrees that it shall be liable for any settlement of any
Proceeding effected without its written consent if (i) such settlement is
entered into more than 60 business days after receipt by such indemnifying party
of the aforesaid request, (ii) such indemnifying party shall not have reimbursed
the indemnified party in accordance with such request prior to the date of such
settlement and (iii) such indemnified party shall have given the indemnifying
party at least 30 days' prior notice of its intention to settle. No indemnifying
party shall, without the prior written consent of the indemnified party, effect
any settlement of any pending or threatened

                                       27


Proceeding in respect of which any indemnified party is or could have been a
party and indemnity could have been sought hereunder by such indemnified party,
unless such settlement includes an unconditional release of such indemnified
party from all liability on claims that are the subject matter of such
Proceeding and does not include an admission of fault, culpability or a failure
to act, by or on behalf of such indemnified party.

         (b) Each Underwriter severally agrees to indemnify, defend and hold
harmless the Company, its trustees, officers, employees and agents, and any
person who controls the Company within the meaning of Section 15 of the Act, or
Section 20 of the Exchange Act, from and against any loss, damage, expense,
liability or claim (including the reasonable cost of investigation) which,
jointly or severally, the Company or any such person may incur under the Act,
the Exchange Act, or common law or otherwise, insofar as such loss, damage,
expense, liability or claim arises out of or is based upon any untrue statement
or alleged untrue statement of a material fact contained in and in conformity
with information furnished by or on behalf of such Underwriter through you to
the Company expressly for use with reference to such Underwriter in the
Registration Statement, the Basic Prospectus, any Prepricing Prospectus, the
Prospectus Supplement or in the Prospectus (or in any of the foregoing as such
document may at any time be amended or supplemented) or arises out of or is
based upon any omission or alleged omission to state a material fact in
connection with such information required to be stated in the Registration
Statement, the Basic Prospectus, any Prepricing Prospectus, the Prospectus
Supplement or the Prospectus (or in any of the foregoing as such document may at
any time be amended or supplemented) or necessary to make such information not
misleading.

         If any Proceeding is brought against the Company or any such person in
respect of which indemnity may be sought against any Underwriter pursuant to the
foregoing paragraph, the Company or such person shall promptly notify such
Underwriter in writing of the institution of such Proceeding and such
Underwriter shall assume the defense of such Proceeding, including the
employment of counsel reasonably satisfactory to such indemnified party and
payment of all fees and expenses, PROVIDED, HOWEVER, that the omission to so
notify such Underwriter shall not relieve such Underwriter from any liability
which such Underwriter may have to the Company or any such person or otherwise.
The Company or such person shall have the right to employ its own counsel in any
such case, but the fees and expenses of such counsel shall be at the expense of
the Company or such person unless the employment of such counsel shall have been
authorized in writing by such Underwriter in connection with the defense of such
Proceeding or such Underwriter shall not have employed counsel to have charge of
the defense of such Proceeding or such indemnified party or parties shall have
reasonably concluded that there may be defenses available to it or them which
are different from or additional to or in conflict with those available to such
Underwriter (in which case such Underwriter shall not have the right to direct
the defense of such Proceeding on behalf of the indemnified party or parties,
but such Underwriter may employ counsel and participate in the defense thereof
but the fees and expenses of such counsel shall be at the expense of such
Underwriter), in any of which events such fees and expenses shall be borne by
such Underwriter and paid as incurred (it being understood, however, that such
Underwriter shall not be liable for the expenses of more than one separate
counsel (in addition to any local counsel) in any one Proceeding or series of
related Proceedings in the same jurisdiction representing the indemnified
parties who are parties to such Proceeding). No Underwriter shall be liable for
any settlement of any such Proceeding effected without the written consent of
such Underwriter but if settled with the written consent of such Underwriter,

                                       28


such Underwriter agrees to indemnify and hold harmless the Company and any such
person from and against any loss or liability by reason of such settlement.
Notwithstanding the foregoing sentence, if at any time an indemnified party
shall have requested an indemnifying party to reimburse the indemnified party
for fees and expenses of counsel as contemplated by the second sentence of this
paragraph, then the indemnifying party agrees that it shall be liable for any
settlement of any Proceeding effected without its written consent if (i) such
settlement is entered into more than 60 business days after receipt by such
indemnifying party of the aforesaid request, (ii) such indemnifying party shall
not have reimbursed the indemnified party in accordance with such request prior
to the date of such settlement and (iii) such indemnified party shall have given
the indemnifying party at least 30 days' prior notice of its intention to
settle. No indemnifying party shall, without the prior written consent of the
indemnified party, effect any settlement of any pending or threatened Proceeding
in respect of which any indemnified party is or could have been a party and
indemnity could have been sought hereunder by such indemnified party, unless
such settlement includes an unconditional release of such indemnified party from
all liability on claims that are the subject matter of such Proceeding.

         (c) If the indemnification provided for in this Section 9 is
unavailable to an indemnified party under subsections (a) and (b) of this
Section 9 in respect of any losses, damage, expenses, liabilities or claims
referred to therein, then each applicable indemnifying party, in lieu of
indemnifying such indemnified party, shall contribute to the amount paid or
payable by such indemnified party as a result of such losses, damages, expenses,
liabilities or claims (i) in such proportion as is appropriate to reflect the
relative benefits received by the Company on the one hand and the Underwriters
on the other hand from the offering of the Shares or (ii) if the allocation
provided by clause (i) above is not permitted by applicable law, in such
proportion as is appropriate to reflect not only the relative benefits referred
to in clause (i) above but also the relative fault of the Company on the one
hand and of the Underwriters on the other in connection with the statements or
omissions which resulted in such losses, damages, expenses, liabilities or
claims, as well as any other relevant equitable considerations. The relative
benefits received by the Company on the one hand and the Underwriters on the
other shall be deemed to be in the same respective proportion as the total
proceeds from the offering (net of underwriting discounts and commissions but
before deducting expenses) received by the Company and the total underwriting
discounts and commissions received by the Underwriters, bear to the aggregate
public offering price of the Shares. The relative fault of the Company on the
one hand and of the Underwriters on the other shall be determined by reference
to, among other things, whether the untrue statement or alleged untrue statement
of a material fact or omission or alleged omission relates to information
supplied by the Company or by the Underwriters and the parties' relative intent,
knowledge, access to information and opportunity to correct or prevent such
statement or omission. The amount paid or payable by a party as a result of the
losses, damages, expenses, liabilities and claims referred to in this subsection
shall be deemed to include any legal or other fees or expenses reasonably
incurred by such party in connection with investigating, preparing to defend or
defending any claim or Proceeding.

         (d) The Company and the Underwriters agree that it would not be just
and equitable if contribution pursuant to this Section 9 were determined by pro
rata allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation that does not take account of the
equitable considerations referred to in subsection (c) above. Notwithstanding
the provisions of this Section 9, no Underwriter shall be required to

                                       29


contribute any amount in excess of the amount by which the total price at which
the Shares underwritten by such Underwriter and distributed to the public were
offered to the public exceeds the amount of any damage which such Underwriter
has otherwise been required to pay by reason of such untrue statement or alleged
untrue statement or omission or alleged omission. No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Act) shall be
entitled to contribution from any person who was not guilty of such fraudulent
misrepresentation. The Underwriters' obligations to contribute pursuant to this
Section 9 are several in proportion to their respective underwriting commitments
and not joint.

         (e) The indemnity and contribution agreements contained in this Section
9 and the covenants, warranties and representations of the Company contained in
this Agreement shall remain in full force and effect regardless of any
investigation made by or on behalf of any Underwriter, its partners, directors,
officers, employees or agents or any person (including each partner, officer,
director, employee or agent of such person) who controls any Underwriter within
the meaning of Section 15 of the Act or Section 20 of the Exchange Act, or by or
on behalf of the Company, its trustees, officers, employees or agents or any
person who controls the Company within the meaning of Section 15 of the Act or
Section 20 of the Exchange Act, and shall survive any termination of this
Agreement or the issuance and delivery of the Shares. The Company and each
Underwriter agree promptly to notify each other of the commencement of any
Proceeding against it and, in the case of the Company, against any of the
Company's officers, trustees, employees or agents in connection with the
issuance and sale of the Shares, or in connection with the Registration
Statement or Prospectus.

         10. NOTICES. Except as otherwise herein provided, all statements,
requests, notices and agreements shall be in writing or by telegram and, if to
the Underwriters, shall be sufficient in all respects if delivered or sent to
UBS Warburg LLC, 299 Park Avenue, New York, New York 10171, Attention: Syndicate
Department, with a copy to Dewey Ballantine LLP, 1301 Avenue of the Americas,
New York, New York 10019, Attention: Frederick W. Kanner, and if to the Company,
shall be sufficient in all respects if delivered or sent to the Company at the
offices of the Company at 400 Centre Street, Newton, Massachusetts 02458,
Attention: David J. Hegarty, President and Chief Operating Officer, with a copy
to Sullivan & Worcester LLP, One Post Office Square, Boston, Massachusetts
02109, Attention: Alexander A. Notopoulos, Jr., Esq.

         11. GOVERNING LAW; CONSTRUCTION. This Agreement and any claim,
counterclaim or dispute of any kind or nature whatsoever arising out of or in
any way relating to this Agreement (a "CLAIM"), directly or indirectly, shall be
governed by, and construed in accordance with, the laws of the State of New
York. The Section headings in this Agreement have been inserted as a matter of
convenience of reference and are not a part of this Agreement.

         12. SUBMISSION TO JURISDICTION. Except as set forth below, no Claim may
be commenced, prosecuted or continued in any court other than the courts of the
State of New York located in the City and County of New York or in the United
States District Court for the Southern District of New York, which courts shall
have jurisdiction over the adjudication of such matters, and the Company
consents to the jurisdiction of such courts and personal service with respect
thereto. The Company hereby consents to personal jurisdiction, service and venue
in any court in which any Claim arising out of or in any way relating to this
Agreement is brought by any third party against an Underwriter or any
indemnified party. Each Underwriter and the

                                       30


Company (on its behalf and, to the extent permitted by applicable law, on behalf
of its stockholders and affiliates) waives all right to trial by jury in any
action, proceeding or counterclaim (whether based upon contract, tort or
otherwise) in any way arising out of or relating to this Agreement. The Company
agrees that a final judgment in any such action, proceeding or counterclaim
brought in any such court shall be conclusive and binding upon the Company and
may be enforced in any other courts in the jurisdiction of which the Company is
or may be subject, by suit upon such judgment.

         13. PARTIES AT INTEREST. The Agreement herein set forth has been and is
made solely for the benefit of the Underwriters, the Company and to the extent
provided in Section 9 hereof the controlling persons, directors and officers
and, if applicable, trustees referred to in such Section, and their respective
successors, assigns, heirs, personal representatives and executors and
administrators. No other person, partnership, association or corporation
(including a purchaser, as such purchaser, from any of the Underwriters) shall
acquire or have any right under or by virtue of this Agreement.

         14. INFORMATION FURNISHED BY THE UNDERWRITERS. The statements set forth
in the last sentence on the last paragraph on the cover page of the Prospectus
Supplement and the statements set forth in the first, third, fifth and seventh
paragraphs under the caption "Underwriting" in the Prospectus Supplement
constitute the only information furnished by or on behalf of the Underwriters as
such information is referred to in Sections 3 and 9 hereof.

         15. COUNTERPARTS. This Agreement may be signed by the parties in one or
more counterparts that together shall constitute one and the same agreement
among the parties.

         16. SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon the
Underwriters, the Company and their respective successors and assigns and any
successor or assign of any substantial portion of the Company's and any of the
Underwriters' respective businesses and/or assets.

         17. MISCELLANEOUS. UBS Warburg LLC, an indirect, wholly-owned
subsidiary of UBS AG, is not a bank and is separate from any affiliated bank,
including any U.S. branch or agency of UBS Warburg LLC. Because UBS Warburg LLC
is a separately incorporated entity, it is solely responsible for its own
contractual obligations and commitments, including obligations with respect to
sales and purchases of securities. Securities sold, offered or recommended by
UBS Warburg LLC are not deposits, are not insured by the Federal Deposit
Insurance Corporation, are not guaranteed by a branch or agency, and are not
otherwise an obligation or responsibility of a branch or agency.

         A lending affiliate of UBS Warburg LLC may have lending relationships
with issuers of securities underwritten or privately placed by UBS Warburg LLC.
To the extent required under the securities laws, prospectuses and other
disclosure documents for securities underwritten or privately placed by UBS
Warburg LLC will disclose the existence of any such lending relationships and
whether the proceeds of the issue will be used to repay debts owed to affiliates
of UBS Warburg LLC.

                                       31


         THE ARTICLES OF AMENDMENT AND RESTATEMENT ESTABLISHING SENIOR HOUSING
PROPERTIES TRUST, DATED SEPTEMBER 2, 1999, A COPY OF WHICH, TOGETHER WILL ALL
AMENDMENTS THERETO, IS DULY FILED IN THE OFFICE OF THE DEPARTMENT OF ASSESSMENTS
AND TAXATION OF THE STATE OF MARYLAND, PROVIDES THAT THE NAME "SENIOR HOUSING
PROPERTIES TRUST" REFERS TO THE TRUSTEES UNDER THE DECLARATION OF TRUST, BUT NOT
INDIVIDUALLY OR PERSONALLY, AND THAT NO TRUSTEE, OFFICER, SHAREHOLDER, EMPLOYEE
OR AGENT OF SENIOR HOUSING PROPERTIES TRUST SHALL BE HELD TO ANY PERSONAL
LIABILITY, FOR ANY OBLIGATION OF, OR CLAIM AGAINST, SENIOR HOUSING PROPERTIES
TRUST. ALL PERSONS DEALING WITH SENIOR HOUSING PROPERTIES TRUST, SHALL LOOK ONLY
TO THE ASSETS OF SENIOR HOUSING PROPERTIES TRUST FOR THE PAYMENT OF ANY SUM OR
THE PERFORMANCE OF ANY OBLIGATION.




                                       32


         If the foregoing correctly sets forth the understanding between the
Company and the Underwriters, please so indicate in the space provided below for
the purpose, whereupon this letter and your acceptance shall constitute a
binding agreement between the Company and the Underwriters severally.

                                     Very truly yours,

                                     SENIOR HOUSING PROPERTIES TRUST

                                     By:
                                        ---------------------------------------
                                        Name:
                                        Title:

Accepted and agreed to as of the date first above written:

UBS WARBURG LLC
MERRILL LYNCH, PIERCE, FENNER & SMITH
      INCORPORATED
A.G. EDWARDS & SONS, INC.
CANTOR FITZGERALD & CO.
FIRST UNION SECURITIES, INC.
LEGG MASON WOOD WALKER, INCORPORATED
TUCKER ANTHONY INCORPORATED

By: UBS WARBURG LLC

By:
   --------------------------------
   Name:
   Title:

By:
   --------------------------------
   Name:
   Title:


                                       33


                                   SCHEDULE A



                                                                                                    Number of
UNDERWRITER                                                                                        FIRM SHARES
                                                                                                
UBS Warburg LLC.................................................................................     2,675,000
Merrill Lynch, Pierce, Fenner & Smith Incorporated..............................................     2,675,000
A.G. Edwards & Sons, Inc........................................................................     2,000,000
First Union Securities, Inc. ...................................................................     2,000,000
Legg Mason Wood Walker, Incorporated............................................................     2,000,000
Tucker Anthony Incorporated.....................................................................     1,000,000
Cantor Fitzgerald & Co..........................................................................       650,000
                                                                                                  -------------
                                            Total................................................   13,000,000
                                                                                                  =============


                                  Schedule A-1



                                   SCHEDULE B

SUBSIDIARY NAME

Five Star Quality Care, Inc.
HRES1 Properties Trust
HRES2 Properties Trust
SHOPCO-AZ, LLC
SHOPCO-CA, LLC
SHOPCO-COLORADO, LLC
SHOPCO-CT, LLC
SHOPCO-GA, LLC
SHOPCO-IA, LLC
SHOPCO-KS, LLC
SHOPCO-MI, LLC
SHOPCO-MO, LLC
SHOPCO-NE, LLC
SHOPCO-SD, LLC
SHOPCO-WI, LLC
SHOPCO-WY, LLC
SNH-CALIFORNIA, INC.
SNH Capital Trust Holdings
SNH Capital Trust I
SNH Capital Trust II
SNH Capital Trust III
SNH/CSL Properties Trust
SNH-IOWA, INC.
SNH Holding Co., Inc.
SNH-MICHIGAN, INC.
SNH-NEBRASKA, INC.
SPTGEN Properties Trust
SPTIHS Properties Trust
SPTMISC Properties Trust
SPTMNR Properties Trust
SPTMRT Properties Trust
SPTSUN Properties Trust
SPTSUN II Properties Trust

                                  Schedule B-1



                                   SCHEDULE C

MATERIAL SUBSIDIARIES

HRES1 Properties Trust
SPTMRT Properties Trust



                                  Schedule C-1



                                   SCHEDULE D

MARYLAND SUBSIDIARIES

Five Star Quality Care, Inc.
HRES1 Properties Trust
HRES2 Properties Trust
SNH Capital Trust Holdings
SNH Capital Trust I
SNH Capital Trust II
SNH Capital Trust III
SNH/CSL Properties Trust
SPTGEN Properties Trust
SPTIHS Properties Trust
SPTMISC Properties Trust
SPTMNR Properties Trust
SPTMRT Properties Trust
SPTSUN Properties Trust
SPTSUN II Properties Trust


                                  Schedule D-1