EXHIBIT 99

Pursuant to the terms of the Operating Agreement of Tri-State Network
Management, L.L.C. dated February 17, 1998 among PhyMatrix Management Company,
Inc. ("Management"), Beth Israel Medical Center and Landmark Physicians
Organization, L.L.C. Management agreed that PhyMatrix Corp. would file the
following section of said Agreement as an exhibit to its Annual Report on Form
10-K.


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3.4 Exclusivity.

    (a) Restrictive Covenants.

        (i) Control. The term "control" shall mean the possession, directly or
indirectly, of the power to direct or cause the direction of any Person, whether
through the ownership of voting securities, by contract or otherwise. Without
limiting the generality of the foregoing, (x) a Person shall be deemed to
control another Person if such Person (1) beneficially owns twenty-five percent
(25%) or more of the outstanding equity securities of such other Person, (2)
beneficially owns or controls twenty-five percent (25%) or more of the
outstanding voting power of such other Person entitled to vote on matters
generally or to vote for the election of members of the board of directors or
other body having similar functions, or, (3) is a general partner or managing
member or has similar authority with respect to such other Person; and (y)
Abraham D. Gosman shall be deemed to control any Person in which Mr. Gosman, any
member of Mr. Gosman's family, any trust for the benefit of Mr. Gosman or any
member of his family, or any entity that is directly or indirectly controlled by
Mr. Gosman or a member of his family, individually or collectively, (1)
beneficially own or control a larger percentage of the outstanding equity
securities of such other Person than any other entity or individual, or (2)
beneficially own or control a larger percentage of the outstanding voting power
of such other Person entitled to vote on matters generally or to vote for the
election of members of the board of directors or other body having similar
functions, than any other entity or individual.

        (ii) Beth Israel. (A) Neither Beth Israel nor any entity controlled by
Beth Israel shall, without PhyMatrix's written consent (which may be withheld in
its sole discretion): (1) Sell any assets used in connection with the Managed
Sites (as defined in Annex A attached hereto) to any Competing Business (as
herein defined), (2) engage in the provision of professional medical services
for or on behalf of a Competing Business, or permit a Competing Business to
manage in any fashion the Managed Sites or any medical 


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practice owned or operated by Beth Israel (other than facilities licensed under
Article 28 of the New York Public Health Law), or act as an agent or consultant
to a Competing Business with respect to such Competing Business's practice
management activities or risk contract management services; provided, however,
that Beth Israel shall not be prohibited from participating solely as a practice
provider in a managed care or other healthcare delivery network, including,
without limitation, any such network that is operated or managed by a Competing
Business. "Competing Business", as used herein, shall mean any business or
enterprise, except for Beth Israel and its majority owned or controlled
subsidiaries, generally recognized to be a competitor of PhyMatrix or any of
PhyMatrix's Affiliates in the provision of practice management services,
including without limitation, the following: any management company or
management service organization; any business substantially engaged in the
management of persons or entities involved in the provision or operation of
medical services; or any management services organization which contracts with
physicians or other health care providers; or any other business substantially
engaged in the management of primary care and/or specialty care physician
offices. For the purposes hereof, St. Lukes-Roosevelt Hospital Center shall be
considered a Competing Business with respect to any practice management services
or management service organization function it may provide. Nothing set forth in
this Section 3.4(a)(ii) shall be construed as including in the definition of
Competing Business the activities of a business or enterprise relating to the
management of risk contracts for physician and facility networks.
Notwithstanding anything to the contrary in this Section 3.4(a)(ii), Beth Israel
shall not be in violation of this Section 3.4(a)(ii) with regard to: (w) the
agreements set forth on Exhibit C attached to the PMA; (x) agreements for
routine billing and collection services which cover only sites other than
Managed Sites; (y) any agreement or joint venture it may enter into with
community health centers or similar facilities that predominately service
medicaid-eligible populations; and (z) hospitals, health facilities, medical
practices, physicians, or other entities now or hereafter owned, employed, or
controlled by Beth Israel ("Controlled Entities") as to which Beth Israel shall
have used its reasonable good faith efforts and shall have afforded PhyMatrix a
reasonable good faith opportunity to convince any such Controlled Entity to have
PhyMatrix provide practice


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management services to such Controlled Entity, if any such Controlled Entity
refuses to agree to have PhyMatrix render such practice management services and
engages a Competing Business to provide such services.

            (B) Beth Israel agrees that neither Beth Israel, nor any Person who
is an Affiliate of Beth Israel on the Effective Date of this Operating
Agreement, shall, directly or indirectly, whether as an owner, investor, partner
or member, without the written consent of PhyMatrix (which may be withheld in
PhyMatrix's sole discretion), participate with another hospital or hospital
system or any Affiliate thereof in the ownership or management of a management
services organization or other Person that controls, operates, manages or
provides risk contract management services (other than by participating solely
as a practice provider in a managed care or other health care delivery network)
to physician practices in New York County, Kings County or Westchester County
(said Counties constituting the "Restricted Zone"), except for the St.
Luke's-Roosevelt Hospital Center ("SLRHC"), but in that case only with respect
to services provided to SLRHC-affiliated physicians.

        (iii) PhyMatrix. PhyMatrix agrees that, without the written consent of
Beth Israel (which may be withheld in Beth Israel's sole discretion), neither
it, PhyMatrix Corp. nor any of their respective Affiliates shall (and PhyMatrix
and PhyMatrix Corp. shall cause each of their Affiliates not to), directly or
indirectly, whether as an agent, independent contractor, owner, investor,
partner, member, consultant, advisor or in any other capacity or relationship:

            (A) operate, manage or provide risk contract management services to
any physicians, IPAs, or medical group practices if (a) such physicians, IPAs,
or medical group practices own, control or manage, or are employed, managed,
owned or controlled by, or are under common ownership, control or management
with, directly or indirectly, a hospital or hospital system or any Affiliate
thereof and (b) such physician, IPA, medical group practice, or hospital or
hospital system is located in whole or in material part within the Restricted
Zone (except for University Physicians Group, P.C., a New York professional
corporation); provided, however, that nothing herein shall prohibit PhyMatrix,


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PhyMatrix Corp. and their respective Affiliates from controlling, operating,
managing, advising or providing risk contract management services to any
physicians, IPAs, or medical group practices that do not own, control or
manage, or are not employed, managed, owned or controlled by, or are not under
common ownership, control or management with, directly or indirectly, a hospital
or hospital system or any Affiliate thereof; or

            (B) participate with a hospital or hospital system or any Affiliate
thereof (or an entity which is the primary manager of a hospital or a hospital
system), other than Beth Israel, in a management services organization or other
Person that operates, manages or provides risk contract management services to
physician practices within the Restricted Zone, except Staten Island University
Hospital.

        (iv) As a specific example of the restrictions contained in Section
3.4(a)(iii) hereof and without limitation thereof, PhyMatrix and PhyMatrix Corp.
agree that neither of them nor any of their Affiliates shall (and PhyMatrix and
PhyMatrix Corp. shall cause each of their Affiliates not to), directly or
indirectly: (x) acquire, enter into a joint venture or common enterprise, buy or
lease all or any material assets, lend money, invest in, buy, accept or obtain
or agree to buy, accept or obtain the capital stock or other securities or the
voting rights thereof (or any right to acquire the capital stock, other
securities or such voting rights), with, to or from any Person, if such Person,
directly or indirectly, engages in (or to the knowledge of PhyMatrix, PhyMatrix
Corp. or any of their Affiliates, intends or plans to engage in) any activities,
such that if such Person were PhyMatrix, such Person would violate Section
3.4(a)(iii) hereof, (y) sell or lease all or any material portion of its assets,
borrow money, sell, issue, grant or agree to sell, issue or grant any of its
capital stock or other securities or the voting rights thereof (or right to
acquire the capital stock, other securities or such voting rights), to or from
any Person, if such Person, directly or indirectly, engages in (or to the
knowledge of PhyMatrix, PhyMatrix Corp. or any of their Affiliates, intends or
plans to engage in) any activities, such that if such Person were PhyMatrix,
such Person would violate Section 3.4(a)(iii) hereof, or (z) merger or
consolidate with, to or into, or agree to merge or consolidate with, to or into,
any Person, if such Person, directly or indirectly, engages in (or to the
knowledge of PhyMatrix, PhyMatrix 


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Corp. or any of their Affiliates, intends or plans to engage in) any activities,
such that if such Person were PhyMatrix, such Person would violate Section
3.4(a)(iii) hereof.

        Notwithstanding the foregoing, it shall not be a violation of Section
3.4(a)(iii) hereof, if PhyMatrix, PhyMatrix Corp. or any of their respective
Affiliates is acquired by a Person, and such Person directly or indirectly
provides services that would be prohibited pursuant to Section 3.4(a)(iii)
hereof, to an aggregate of no more than 100 physicians in the entire Restricted
Zone (e.g., if there are 75 physician providers under contract with an IPA to
which such services are provided, it shall be deemed that 75 physicians are
included in the foregoing computation). Physicians who are radiologists,
anesthesiologists, or pathologists, shall not be included in the foregoing
computation of the aggregate number of physicians provided services in the
Restricted Zone. In no event, however, shall such acquiror, at the time of the
acquisition, or PhyMatrix, PhyMatrix Corp. or their Affiliates, inclusive of
such acquiror, at any time after the acquisition (a) provide risk contract
management services in violation of Section 3.4(a)(iii) hereof, or (b) provide
services that would be prohibited by Section 3.4(a)(iii) hereof to more than 100
physicians in the aggregate in the Restricted Zone, exclusive of radiologists,
anesthesiologists, and pathologists.

        (v) PhyMatrix, PhyMatrix Corp. (and their Affiliates) are hereby 
independently obligated as follows:

            (A) To immediately inform Beth Israel in writing of (1) any
violation of any of the restrictions herein, or (2) any event or occurrence that
to the knowledge of PhyMatrix, PhyMatrix Corp. or their Affiliates would
reasonably be expected to result in a violation of the restrictions herein over
time in the normal course.

            (B) Neither PhyMatrix, PhyMatrix Corp. nor any of their Affiliates,
nor any of their respective directors, members, officers, employees, agents or
representatives will, directly or indirectly, solicit, initiate or facilitate
(including by way of furnishing or disclosing non-public information) any
inquiries or the making of any proposal with respect to any merger,
consolidation or other business combination, contract or other arrangement or
relationship involving PhyMatrix or PhyMatrix Corp. (or any of their 


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Affiliates), or the acquisition, lease or use of all or any significant assets
or capital stock thereof (a "Transaction"), or negotiate with any Person with
respect to any Transaction, or enter into any agreement, arrangement or
understanding with respect to any Transaction, if by a reasonable understanding
of the substance of the proposed Transaction, the restrictions contained in this
Section 3.4(a) would be violated either in connection with the consummation of
such Transaction, or in the normal course thereafter.

            (C) To take all actions as are reasonably necessary to prevent any
event or occurrence that would reasonably be expected to result in a violation
of the restrictions herein over time in the normal course.

            (D) To (1) file a copy of this Section 3.4(a) and such other terms
of this Operating Agreement as PhyMatrix or PhyMatrix Corp. deems reasonably
necessary with the Securities and Exchange Commission (the "SEC") on PhyMatrix
Corp.'s Form 8-K within 15 days of the execution and delivery of this Operating
Agreement and in each filing with the SEC in which material contracts are
required to be filed as exhibits and (2) describe the material terms of this
Section 3.4 in PhyMatrix Corp.'s Annual Reports on Form 10-K for its 1997, 1998
and 1999 fiscal years and (either directly or by incorporation by reference) in
the prospectus portion of each registration statement filed or used by it prior
to December 31, 1997.