<PAGE>

                                                                   Exhibit 10.23
                                                                   -------------


                                   AGREEMENT


    Agreement entered into as of November 30, 1997 by and among Physicians
Quality Care, Inc., a Delaware corporation ("PQC"), Flagship Health, P.A., a
Maryland professional association ("Flagship I"), Flagship Health II, P.A.
("Flagship II" and collectively with Flagship I, "Flagship"), and the physicians
listed on the signature page of this Agreement who are former stockholders and
optionholders (the "Stockholders") of Clinical Associates, a Maryland
professional association.

    This Agreement provides for certain understandings between the Stockholders,
PQC and Flagship in connection with the Amended and Restated Services Agreement
between PQC and Flagship and the Employment Agreements between each Stockholder
and Flagship.

    Now, therefore, in consideration of the representations, warranties and
covenants herein contained, the parties agree as follows.  Capitalized terms
used in this Agreement and not defined in this Agreement shall have the meaning
assigned to them in the Services Agreement.

    1.  Addition of Founding Medical Group Physicians to Additional Pod
        ---------------------------------------------------------------
Compensation Model.  The Services Agreement provides for a different
------------------
compensation methodology for the Founding Pods and the Additional Pods.  As a
part of their long-term business goals,  PQC and Flagship may determine that it
is in their best interest to merge the compensation arrangements of the Founding
Pods into the compensation arrangements for the Additional Pods.  While PQC and
Flagship shall have no obligation to do so, PQC and Flagship shall have the
right to amend the Services Agreement, including Appendices B-1 and B-2 thereto,
to merge the compensation arrangements of the Founding Pods into the
compensation arrangements for the Additional Pods; provided that such merger and
its material terms are approved by PQC and two-thirds of the Stockholders who
continue to be Medical Group Physicians at such time.  In the event that the
compensation arrangements for the Founding Pods and the Additional Pods are
merged, PQC shall provide a guarantee (which shall be in a form acceptable to
two-thirds of the Stockholders, acting reasonably) to the Stockholders that for
a two year period (commencing on the date of the merger of the compensation
arrangements for at least ten physicians in one or more Founding Pods into the
compensation arrangements for the Additional Pods) that the compensation of each
Stockholders who continues to be a Medical Group Physician will not be less than
the Physician Draw for such Stockholders as in effect at the time of such
merger; provided that the guarantee shall provide for reduction of the
guaranteed Physician Draw for the Stockholders  to reflect declines, if any, in
productivity and billing.  At the end of the two-year period covered by the
guarantee, the Services Agreement shall be amended, if requested by two-thirds
of the members of the Management Committee, to establish a separate Medical
Group Account and Compensation Pool with respect to Pod R.

    2.  Option to Amend Purchase Price.  Within six months after the Effective
        ------------------------------
Date, the Stockholders, by the approval of two-thirds of the Stockholders, shall
have the right to elect to receive up to an additional 2,000,000 shares of Class
<PAGE>

A Common Stock of PQC (the "Common Stock") as additional consideration for the
merger of Clinical Associates into Flagship.  As a condition to receipt of such
additional shares, the Stockholders must agree to amend, effective upon delivery
of such Common Stock, the Services Agreement and their Employment Agreements so
that an additional $760,000 (or such proportionately reduced amount if less than
2,000,000 shares of Common Stock are elected) with respect to each fiscal year
is payable to PQC from the amount that would otherwise be allocated pursuant to
Appendix B-2 of the Services Agreement to the Additional Pod Medical Group
Account.

    3.  Right to Additional Compensation in the Event of a Shortfall.  With
        --------------------------------------------------------------
respect to each fiscal year during the Shortfall Period (as defined below), the
amount that would have been allocated to PQC pursuant to Appendix B-2 of the
Services Agreement shall be reduced by the Adjustment Amount and the amount that
is allocated to the Additional Pod Medical Group Account shall be increased by
the Adjustment Amount; provided, however, that if with respect to any fiscal
year there is no Shortfall (as defined below) or PQC completes a public offering
of its Common Stock at a price to the public of $9.00 or more per share, this
Section 3 shall be of no further effect and no further adjustment shall be made
pursuant to this Section 3 during any subsequent fiscal year. "Shortfall Period"
shall mean every fiscal year commencing after December 31, 1997 to and including
the earlier of (i) the first fiscal year in which there is no Shortfall or (ii)
the fiscal year immediately preceding the date of the closing of a public
offering of Common Stock with a price to the public of $9.00 or more.
"Shortfall" shall mean the difference, if a positive amount, between $3 million
and the aggregate increase in Net Adjusted Billings over Baseline Net Adjusted
Billings by the specialist physicians in any Additional Pod; provided, however,
that there shall not be deemed to be a Shortfall in the event that there is less
than $3 million increase in Net Adjusted Billings because the specialist
physicians in the Additional Pods do not have the capacity to accept (unless the
Additional Pods are attempting in good faith to add physicians with the
applicable speciality and do add such additional capacity within six months of
notification from PQC), or were otherwise unwilling to accept (provided that PQC
shall give the Management Committee one month to cure any such unwillingness to
accept new patients if such refusals to accept new patients are isolated
occurrences and are not recurring), such referrals.  "Adjustment Amount" with
respect to any fiscal year shall be equal to (i) 45% of the Shortfall for such
fiscal year less the Laboratory Allocation.  The Laboratory Allocation with
respect to each fiscal year shall be equal to the Net Margin from Laboratory
Services allocated to Pod R under the Services Agreement.  The amount of any
Shortfall, Laboratory Allocation and Adjustment Amount shall be calculated as
soon as practicable after the end of each fiscal year.  Any reallocation on the
basis of an Adjustment Amount shall be made on or prior to the date that the
Additional Pod Medical Group Account is to be distributed to the physicians in
the Additional Pods under the Services Agreement.

    4.  Option to Sell Shares to PQC.  In the event that on the fourth
        ----------------------------
anniversary of the Effective Date PQC has not completed an underwritten initial
public offering, each Stockholder shall have the right to require PQC to
repurchase the Common Stock issued to such Stockholder pursuant to the Merger
Agreement at a purchase price of $3.00 per share (subject to adjustment for

                                      -2-
<PAGE>

stock splits and combination).  PQC shall have the right to pay the purchase
price in the form of a five (5) year non-interest bearing note.  The principal
payable with respect to each such note issued to a Stockholder shall be reduced
each year that the note is outstanding by the amount, if any, that such
Stockholder=s compensation from Flagship during such year exceeds the
Stockholders' Physician Draw for such year.  The election to have PQC repurchase
the Common Stock must be made within 45 days of the fourth anniversary of the
Effective Date.

    5.  Board Representation.  PQC agrees that it will use its best efforts to
        --------------------
cause two physicians nominated by the Stockholders to be elected to PQC's Board
of Directors.  In addition, the Stockholders shall be entitled until such time
as PQC completes an initial public offering to appoint a representative who will
have the right to notice of and to be present at regularly scheduled meetings of
the PQC Board.

    6.  Management Services for Pod R.  PQC and Flagship agree that neither PQC
        -----------------------------
nor Flagship shall materially change the billing methodology used on the
Effective Date with respect to Pod R or replace any senior level supervisory
personnel used on the Effective Date by Pod R in billing and collections without
the approval of a majority of the Members of the Management Committee.  PQC and
Flagship also agree not to replace the Flagship Chief Operating Officer or the
Medical Director without the approval of a majority of the members of the Pod R
Management Committee.

    7.  Operating Policies.  PQC and Flagship intend that the operating policies
        -------------------
set forth on Annex A to this Agreement will be adopted by the Joint Policy Board
as soon as practicable after the Effective Date.  PQC agrees that the PQC
Representatives to the Joint Policy Board will vote in favor of the adoption of
such policies.

    8.  Publicity Budget.  PQC and Flagship agree that the Flagship publicity
        --------------
budget for the first twelve months after the Effective Date shall be at least
$1,000,000, $250,000 of which shall be a Practice Expense of Pod R.

    9.  Pod R Management Committee.  The Stockholders agree that Pod R shall
        --------------------------
establish a Management Committee that shall primarily be responsible for
overseeing the relationship between PQC, Flagship and the Medical Group
Physicians assigned to Pod R and for taking the actions expressly contemplated
by this Agreement.  The membership and rules governing the Management Committee
will be determined from time to time by the Medical Group Physicians assigned to
Pod R.  PQC and Flagship agree to work with Pod R in establishing the Management
Committee.

    10.  Certain Changes in Control.  PQC agrees that neither PQC nor Flagship
         -------------------------
will  (i) merge or consolidate with or into, (ii) joint venture with, (iii) sell
or lease all or substantially all of their assets to, (iv) grant governance
participation to, (v) become managed by, or (vi) sell a controlling interest in
the stock of Flagship or PQC to,  a Baltimore Health Care Entity without the
approval of a majority of the members of the Management Committee.  A Baltimore

                                      -3-
<PAGE>

Health Care Entity means any hospital, medical group or other organization that
principally conducts its business in and derives its revenues from the delivery
of healthcare services in Maryland, but shall not include any physician group
that enters into an affiliation transaction with PQC.

    11.  No Third Party Beneficiaries.  This Agreement shall not confer any
         ----------------------------
rights or remedies upon any person other than PQC, Flagship and the Stockholders
and their respective successors and permitted assigns.

    12.  Entire Agreement.  This Agreement (including the documents referred to
         ----------------
herein) constitutes the entire agreement among the parties and supersedes any
prior understandings, agreements, or representations by or among the parties,
written or oral, with respect to the subject matter hereof.

    13.  Counterparts.  This Agreement may be executed in two (2) or more
         ------------
counterparts, each of which shall be deemed an original but all of which
together shall constitute one (1) and the same instrument.

    14.   Headings.  The section headings contained in this Agreement are
          --------
inserted for convenience only and shall not affect in any way the meaning or
interpretation of this Agreement.

    15.  Notices.  All notices, requests, demands, claims, and other
         -------
communications hereunder shall be in writing.  Any notice, request, demand,
claim, or other communication hereunder shall be deemed duly delivered two (2)
business days after it is sent by registered or certified mail, return receipt
requested, postage prepaid, or one (1) business day after it is sent via a
reputable nationwide overnight courier service, in each case to the intended
recipient as set forth below:

If to the Stockholders:
-----------------------

To the last known home address of each Stockholder as maintained in the records
of Flagship with a copy to:

          Epstein, Becker & Green, P.C.
          1227 25th Street, N.W.
          Washington, DC 20037-1156
          Attention:  Mark Lutes, Esq.

                                      -4-
<PAGE>

If to PQC or Flagship:
----------------------

          Physicians Quality Care, Inc.
          950 Winter Street
          Suite 2410
          Waltham, MA  02154
          Attention:  Jerilyn Asher

With a copy to:

          David C. Phelan, Esq.
          Hale and Dorr
          60 State Street
          Boston, MA  02109

Any party may give any notice, request, demand, claim, or other communication
hereunder using any other means (including personal delivery, expedited courier,
messenger service, telecopy, telex, ordinary mail, or electronic mail), but no
such notice, request, demand, claim, or other communication shall be deemed to
have been duly given unless and until it actually is received by the party for
whom it is intended.  Any party may change the address to which notices,
requests, demands, claims, and other communications hereunder are to be
delivered by giving the other Parties notice in the manner herein set forth.

    16.  Governing Law.  This Agreement shall be governed by and construed in
         -------------
accordance with the internal laws (and not the law of conflicts) of the State of
Maryland.

    17.  Amendments and Waivers.  No amendment of any provision of this
         ----------------------
Agreement shall be valid unless the same shall be in writing and signed by PQC,
Flagship and two-thirds of the Stockholders.  No waiver by any party of any
default, misrepresentation, or breach of warranty or covenant hereunder, whether
intentional or not, shall be deemed to extend to any prior or subsequent
default, misrepresentation, or breach of warranty or covenant hereunder or
affect in any way any rights arising by virtue of any prior or subsequent such
occurrence.

    18.  Severability.  If any term, provision, covenant or restriction of this
         ------------
Agreement is held by a court of competent jurisdiction to be invalid, void or
unenforceable, the remainder of the terms, provisions, covenants and
restrictions of this Agreement shall remain in full force and effect and shall
in no way be affected, impaired or invalidated.

    19.  Expenses.  Except as otherwise expressly provided herein, each party to
         --------
this Agreement shall pay its own costs and expenses in connection with the
transactions contemplated hereby.

                                      -5-
<PAGE>

    IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date first above written.


                              PHYSICIANS QUALITY CARE, INC.


                              /s/ Samantha J. Trotman
                              ------------------------------------------
                              By: Samantha J. Trotman
                              Title:  Chief Financial Officer and
                                      Vice President



                              FLAGSHIP HEALTH, P.A.


                              /s/ Dana Frank, M.D.
                              -----------------------------------------
                              By:  Dana Frank, M.D.
                              Title:  President



                              FLAGSHIP HEALTH II, P.A.


                              /s/ Dana Frank, M.D.
                              -----------------------------------------
                              By:  Dana Frank, M.D.
                              Title:  President

                                      -6-
<PAGE>

                                    CLINICAL ASSOCIATES STOCKHOLDERS:


                                    /s/ Mohammed Ahmed
                                    -----------------------------------


                                    /s/ Samuel Akman
                                    --------------------------------------


                                    /s/ Mahmood Alikhan
                                    -------------------


                                    /s/ Robert S. Baxt
                                    ------------------

                                    /s/ George Bedon
                                    ----------------

                                    /s/ Paul Z. Bodnar
                                    ------------------

                                    /s/ William Bouchelle
                                    ---------------------


                                    /s/ James M. Corkum
                                    -------------------


                                    /s/ Albert F. DeLoskey
                                    ----------------------


                                    /s/ James F. Dunlay
                                    -------------------


                                    /s/ Paul J. Edgar
                                    -----------------


                                    /s/ Clara E. Escuder
                                    --------------------


                                    /s/ Carl S. Friedman
                                    --------------------

                                      -7-
<PAGE>

                                    /s/ Miquel A. Frontera
                                    ----------------------


                                    /s/ John Gambrill
                                    -----------------


                                    /s/ Carlton Greene
                                    ------------------


                                    /s/ Gregory Hall
                                    ----------------


                                    /s/ Michael Jacobs
                                    ------------------


                                    /s/ Kenneth P. Judd
                                    -------------------


                                    /s/ Virginia Kranz
                                    ------------------

                                    /s/ Michael Lifson
                                    ------------------


                                    /s/ Richard H. Mack
                                    -------------------


                                    /s/ Richard Maffezzoli
                                    ----------------------


                                    /s/ Gary A. Manko
                                    -----------------


                                    /s/ Steven Miller
                                    -----------------


                                    /s/ Judah A. Minkove
                                    --------------------


                                    /s/ Keiffer J. Mitchell
                                    -----------------------

                                      -8-
<PAGE>

                                    /s/ Charlotte E. Modly
                                    ----------------------


                                    /s/ Rose Mary Mulaikal
                                    ----------------------


                                    /s/ Bindu Noor
                                    --------------


                                    /s/ Bonnie Orzech-Nixon
                                    -----------------------


                                    /s/ James Paskert
                                    -----------------


                                    /s/ Radha Pathak
                                    ----------------


                                    /s/ Robert Peques
                                    -----------------


                                    /s/ Toby Ritterhoff
                                    -------------------


                                    /s/ Bruce Rosenberg
                                    -------------------


                                    /s/ Duncan Salmon
                                    -----------------


                                    /s/ David Saltzberg
                                    -------------------


                                    /s/ Lise K. Satterfield
                                    -----------------------


                                    /s/ Richard T. Scholz
                                    ---------------------


                                    /s/ Sidney Seidman
                                    ------------------

                                      -9-
<PAGE>

                                    /s/ Linda Sevier
                                    ----------------


                                    /s/ David S. Shear
                                    ------------------


                                    /s/ Ronald Sher
                                    ---------------


                                    /s/ Alan M. Shorofsky
                                    ---------------------


                                    /s/ Stephen M. Siegel
                                    ---------------------


                                    /s/ Stuart B. Silver
                                    --------------------


                                    /s/ Edward Souweine
                                    -------------------


                                    /s/ Jonathan E. Surell
                                    ----------------------


                                    /s/ Anthony Vazzano
                                    -------------------


                                    /s/ Barry Vogelstein
                                    --------------------


                                    /s/ Richard Weisman
                                    -------------------


                                    /s/ Julie Winston
                                    -----------------


                                    /s/ Wayland Wong
                                    ----------------


                                    /s/ Robert E. Zadek
                                    -------------------

                                      -10-
<PAGE>

                                    CLINICAL ASSOCIATES
                                    OPTIONHOLDERS:


                                    /s/ William Bartholomay
                                    -----------------------


                                    /s/ Sarah Bodnar
                                    ----------------


                                    /s/ Marla Caplan
                                    ----------------

                                      -11-
<PAGE>

                                    ANNEX A
                                    -------


                             Operational Policies.


    The approval of the Joint Policy Board or the Management Committee of Pod R
will be required prior to PQC authorizing expenditures in excess of budgeted
amounts.

                                      -12-