COMMON STOCK PURCHASE AGREEMENT


                  THIS COMMON STOCK PURCHASE AGREEMENT (this "Agreement"),  made
this 11th day of January,  1999 between Mid Atlantic Medical  Services,  Inc., a
Delaware  corporation  (the  "Seller")  and  The  Bank of New  York,  not in its
individual  or  corporate  capacity,  but solely in its capacity as trustee (the
"Trustee")  of  the  Stock  Compensation  Trust  (the  "Trust")  (the  Trust  is
hereinafter  sometimes  referred to as the "Purchaser")  under a trust agreement
between the Seller and the  Trustee  dated  August 26,  1996,  as most  recently
amended and restated as of January 11, 1999 (the "Trust Agreement").

                              W I T N E S S E T H:

                  WHEREAS, as contemplated by the Trust Agreement, the Purchaser
is to  purchase  from the  Seller,  and the Seller is to sell to the  Purchaser,
shares of the Seller's common stock,  $0.01 par value (the "Common Stock"),  all
as more specifically provided herein;

                  NOW,  THEREFORE,  in consideration of the mutual covenants and
undertakings  contained  herein,  and subject to and on the terms and conditions
herein set forth, the parties hereto agree as follows:

                                    ARTICLE I

                           PURCHASE AND SALE OF SHARES

                  1.1 Purchase and Sale. Subject to the terms and conditions set
forth herein,  the Seller will sell to the  Purchaser,  and the  Purchaser  will
purchase from the Seller, at the Closing (as hereinafter  defined),  one million
five hundred thousand  (1,500,000) shares of Common Stock at $12 per share which
is the Fair Market  Value (as  defined in the Trust) of the Common  Stock on the
last full  trading day prior to the  Closing.  The shares of Common  Stock to be
purchased by the Purchaser and sold by the Seller at the Closing are referred to
in this  Agreement  as the  "Common  Shares."  In  consideration  for the Common
Shares,  the Purchaser will deliver to the Seller cash in the amount of $15,000,
representing  the  par  value  of  the  Common  Stock,  and  an  allonge  to the
Replacement  Promissory Note dated December 20, 1996 previously delivered by the
Purchaser to the Seller in the principal amount of $118,076,287.20  (the "Note")
in the form of Exhibit A attached hereto.

                  1.2  Closing.  The  closing  of the sale and  purchase  of the
Common  Shares  hereunder  (the  "Closing"),  will be held at the offices of the
Seller on January 11, 1999 or at such other time, date and place as agreed to by
the parties.

                  1.3  Delivery and  Payment.  At the  Closing,  the Seller will
deliver to the Purchaser a certificate  representing  the Common  Shares,  which
certificate  shall be registered in the name of the Trustee,  or the name of its
nominee,  against  payment  by the  Purchaser  to the  Seller  of the  aggregate
purchase  price  therefor.   Notwithstanding  the  foregoing,   the  Seller  may
accomplish the transfer of shares to the Trustee by book entry, in which event a
cross  receipt  shall be executed by the parties.  The Seller will pay all stamp
and other  transfer  taxes,  if any, which may be payable in respect of the sale
and delivery of the Common Shares.


                                   ARTICLE II

                  REPRESENTATIONS AND WARRANTIES OF THE SELLER

                  The  Seller  represents  and  warrants  to  the  Purchaser  as
follows:

                  2.1  Corporate  Existence and  Authority.  The Seller (i) is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware;  (ii) has all  requisite  corporate  power to execute,
deliver  and  perform  this  Agreement;   and  (iii)  has  taken  all  necessary
corporation action to authorize the execution,  delivery and performance of this
Agreement.

                  2.2 No Conflict.  The execution and delivery of this Agreement
does not, and the consummation of the transactions contemplated hereby will not,
conflict  with or  constitute a default  under (i) the Seller's  certificate  of
incorporation or by-laws,  (ii) any agreement,  indenture or other instrument to
which the Seller is a party or by which the Seller or its assets may be bound or
(iii)  any law,  regulation,  order,  arbitration,  award,  judgment  or  decree
applicable to the Seller.

                  2.3  Validity.  This  Agreement  has been  duly  executed  and
delivered  by the  Seller  and is a valid and  binding  agreement  of the Seller
enforceable  against  the Seller in  accordance  with its  terms,  except as the
enforceability thereof may be limited by any applicable bankruptcy,  insolvency,
reorganization,  moratorium,  fraudulent  conveyance or other laws affecting the
enforcement of creditors' rights generally, and by general principles of equity.

                  2.4 The  Common  Shares.  The  Common  Shares  have  been duly
authorized  and are (or when  issued as  contemplated  hereby  will be)  validly
issued and  constitute  fully-paid  and  non-assessable  shares of Common Stock,
$0.01 par value, of the Seller.  No stockholder of the Seller has any preemptive
or other  subscription  right to acquire any shares of Common Stock.  The Seller
will convey to the  Purchaser,  on the date of Closing,  good and valid title to
the Common Shares free and clear of any liens,  claims,  security  interests and
encumbrances.

                  2.5 Litigation.  There are no actions,  suits,  proceedings or
arbitrations  or  investigations  pending,  or to the Seller's  best  knowledge,
threatened in any court or before any governmental  agency or instrumentality or
arbitration  panel or otherwise  against or by the Seller which seek to or could
restrain,  prohibit,  rescind  or  declare  unlawful,  or result in  substantial
damages in respect of this  Agreement  or the  performance  hereof by the Seller
(including, without limitation, the delivery of the Common Shares).



                                   ARTICLE III

                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

                  The Purchaser hereby  represents and warrants to the Seller as
follows:

                  3.1  Authority;  Validity.  The  Purchaser  has full power and
authority to execute and deliver this  Agreement  and the Note as Trustee and to
consummate the transactions contemplated hereby. The Note has been duly executed
by the Trustee on behalf of the Trust and,  upon the  execution  and delivery by
the  Trustee  on behalf  of the  Trust,  the Note  will be a valid  and  binding
agreement of the Purchaser  enforceable in accordance with its terms,  except as
the  enforceability  thereof  may  be  limited  by  any  applicable  bankruptcy,
insolvency,  reorganization,  moratorium,  fraudulent  conveyance  or other laws
affecting  the  enforcement  of  creditors'  rights  generally,  and by  general
principles of equity.


                                   ARTICLE IV

                RESTRICTIONS ON DISPOSITION OF THE COMMON SHARES

                  4.1 Restricted Securities. The Purchaser acknowledges that the
Purchaser is acquiring the Common Shares  pursuant to a transaction  exempt from
registration under the 1933 Act. The Purchaser  represents,  warrants and agrees
that all Common Shares acquired by the Purchaser  pursuant to this Agreement are
being  acquired for  investment  without any intention of making a  distribution
thereof,  or of making any sale or other  disposition  thereof which would be in
violation of the 1933 Act or any applicable  state  securities law, and that the
Purchaser  will not dispose of any of the Common  Shares except that the Trustee
will,  from  time  to  time,  convey  a  portion  of the  Common  Shares  to the
participants  in the Plans (as that term is defined in the Trust  Agreement)  to
satisfy the obligations of the Seller thereunder, and except upon termination of
the Trust to the extent  that the Trust then  holds any  Common  Shares,  all in
compliance  with all  provisions of applicable  federal and state law regulating
the issuance, sale and distribution of securities.

                  4.2  Legend.   Until  such  time  as  the  Common  Shares  are
registered  pursuant  to the  provisions  of the 1933 Act,  any  certificate  or
certificates  representing the Common Shares delivered  pursuant to Section 1.3,
will bear a legend in substantially the following form:

                  "The  shares  represented  by this  certificate  have not been
                  registered  under the Securities Act of 1933, as amended,  and
                  may not be sold,  transferred or otherwise  disposed of unless
                  they have  first been  registered  under such Act or unless an
                  exemption from registration is available."

The Seller may place stop transfer  orders against the  registration or transfer
of any shares evidenced by such a certificate or certificates until such time as
the requirements of the foregoing are satisfied.


                                    ARTICLE V

                              CONDITIONS TO CLOSING

                  5.1 Conditions to Obligations of the Purchaser. The obligation
of the Purchaser to purchase the Common Shares is subject to the satisfaction of
the following conditions on the date of Closing:

                           (a) The  representations and warranties of the Seller
                  set forth in Article II hereof shall be true and correct;  and
                  if the  Closing  shall  occur on a date other than the date of
                  this Agreement, the Purchaser shall have been furnished with a
                  certificate, dated the date of Closing, to such effect, signed
                  by an authorized officer of the Seller; and

                           (b)  All  permits,   approvals,   authorizations  and
                  consents of third parties  necessary for the  consummation  of
                  the transactions herein shall have been obtained, and no order
                  of any court or administrative agency shall be in effect which
                  restrains or prohibits the  transactions  contemplated by this
                  Agreement,  and no suit,  action  or other  proceeding  by any
                  governmental  body or other person shall have been  instituted
                  which  questions the validity or legality of the  transactions
                  contemplated by this Agreement.


                  5.2 Conditions to Obligations of the Seller. The obligation of
the Seller to issue,  sell and deliver  the Common  Shares to the  Purchaser  is
subject to the satisfaction of the following conditions on the date of Closing:

                           (a)  The   representations   and  warranties  of  the
                  Purchaser  set forth in Article  III hereof  shall be true and
                  correct;  and if the Closing  shall occur on a date other than
                  the  date  of this  Agreement,  the  Seller  shall  have  been
                  furnished  with a  certificate  dated the date of Closing,  to
                  such effect,  signed by an  authorized  office of the Trustee;
                  and

                           (b) No order of any  court or  administrative  agency
                  shall  be  in  effect  which   restrains   or  prohibits   the
                  transactions  contemplated  by this  Agreement,  and no  suit,
                  action or other proceeding by any  governmental  body or other
                  person shall have been instituted which questions the validity
                  or  legality  of  the   transactions   contemplated   by  this
                  Agreement.


                                   ARTICLE VI

                                  MISCELLANEOUS

                  6.1 Expenses. The Seller shall pay all of its expenses, and it
shall  pay the  Purchaser's  expenses,  in  connection  with the  authorization,
preparation,  execution and  performance of this  Agreement,  including  without
limitation  the  reasonable  fees  and  expenses  of the  Trustee,  its  agents,
representatives, counsel, financial advisors and consultants.

                  6.2 Survival of Seller's  Representations and Warranties.  All
representations  and  warranties  made by the  Seller to the  Purchaser  in this
Agreement shall survive the Closing.

                  6.3  Notices.  All notices,  requests or other  communications
required or permitted to be delivered  hereunder shall be in writing,  delivered
by registered or certified mail, return receipt requested, as follows:

                           (a)      To the Seller:

                                    Sharon Pavlos, Senior Vice
                                      President and General Counsel
                                    Mid Atlantic Medical Services, Inc.
                                    4 Taft Court
                                    Rockville, MD  20850

                           (b)      To the Purchaser:

                                    Richard J. Barry
                                    The Bank of New York
                                    One Wall Street
                                    New York, NY  10286

Any party hereto may from time to time,  by written  notice given as  aforesaid,
designate any other address to which notices,  requests or other  communications
addressed to it shall be sent.

                  6.4 Specific Performance.  The parties hereto acknowledge that
damages would be an inadequate  remedy for any breach of the  provisions of this
Agreement  and agree that the  obligations  of the  parties  hereunder  shall be
specifically  enforceable,  and neither party will take any action to impede the
other from seeking to enforce such rights of specific performance.

                  6.5 Successors and Assigns; Integration;  Assignability.  This
Agreement  shall be binding upon and inure to the benefit of and be  enforceable
by the parties hereto,  and their respective legal  representatives,  successors
and assigns.  This Agreement (a) constitutes,  together with the Note, the Trust
Agreement, and any other written agreements between the Purchaser and the Seller
executed  and  delivered on the date hereof,  the entire  agreement  between the
parties  hereto and supersedes  all other prior  agreements and  understandings,
both  written and oral,  among the parties,  with respect to the subject  matter
hereof;  (b) shall not confer upon any person other than the parties  hereto any
rights or remedies  hereunder;  and (c) shall not be  assignable by operation of
law or otherwise, except that the Trustee may assign all its rights hereunder to
any corporation or other institution  exercising trust powers in connection with
any such institution assuming the duties of a trustee under the Trust.

                  6.6 Governing Law.  This Agreement shall be governed by and
construed in accordance with the laws of the state of New York.

                  6.7 Further  Assurances.  Subject to the terms and  conditions
herein provided, each of the parties hereto agrees to use all reasonable efforts
to take,  or cause to be taken,  all action and to do, or cause to be done,  all
things  necessary,  proper or advisable to  consummate  and make  effective  the
transactions contemplated by this Agreement.

                  6.8  Amendment  and  Waiver.  No  amendment  or  waiver of any
provision of this Agreement or consent to departure therefrom shall be effective
unless in writing and signed by the Purchaser and the Seller.

                  6.9 Counterparts. This Agreement may be executed in any number
of counterparts with the same effect as if the signatures  thereto were upon one
instrument.

                  6.10 Certain  Limitations.  The execution and delivery of this
Agreement  and the  performance  by the Trustee of this  Agreement and under the
terms of the Trust have been or will be, effected by the Trustee in its capacity
as Trustee. Nothing in this Agreement shall be interpreted to increase, decrease
or modify in any manner  any  liability  of the  Trustee to the Seller or to any
trustee,  representative or other claimant by right of the Seller resulting from
the Trustee's performance of its duties under the constituent instruments of the
Trust, and no personal  liability shall be asserted or enforceable  against said
entity  by  reason  of any  of  the  covenants,  statements  or  representations
contained in this Agreement.

                  6.11  Incorporation.  The  terms and  conditions  of the Trust
Agreement relating to the nature of the  responsibilities of the Trustee and the
indemnification  of the  Trustee  by  the  Seller  are  incorporated  herein  by
reference and made applicable to this Agreement.

                  IN WITNESS  WHEREOF,  the undersigned  have duly executed this
Agreement on the date and year first above written.


                                           Mid Atlantic Medical Services, Inc.


                                           By:  /s/ Sharon C. Pavlos
                                           Title:  Senior Vice President, 
                                                   General Counsel



                              The Bank of New York in its capacity as trustee
                               of the Mid Atlantic Medical Services, Inc. Stock
                               Compensation Trust


                                                     By: /s/ Richard J. Barry   
                                                     Title:  Vice President