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                          STOCKHOLDER RIGHTS AGREEMENT

                                  dated as of

                                 April 23, 1997

                                    between

                                   HCIA INC.

                                      and

                            ChaseMellon Shareholder
                                Services, L.L.C.

                                as Rights Agent


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                          STOCKHOLDER RIGHTS AGREEMENT


                               Table of Contents

                                                                            Page
                                                                            ----
                                  Article I
                                 DEFINITIONS

Section 1.1      Definitions................................................   2

                                  Article II
                               THE RIGHTS AGENT

Section 2.1      General....................................................  11
Section 2.2      Merger or Consolidation or Change of Name of
                    Rights Agent............................................  12
Section 2.3      Duties of Rights Agent.....................................  13
Section 2.4      Change of Rights Agent.....................................  17

                                 Article III
                                  THE RIGHTS

Section 3.1      Summary of Rights..........................................  18
Section 3.2      Legend on Common Stock Certificates........................  19
Section 3.3      Exercise of Rights; Separation of Rights...................  19
Section 3.4      Adjustments to Exercise Price; Number of Rights............  23
Section 3.5      Date on Which Exercise is Effective........................  25
Section 3.6      Execution, Authentication, Delivery and Dating of
                 Rights Certificates........................................  26
Section 3.7      Registration, Registration of Transfer and Exchange........  26
Section 3.8      Mutilated, Destroyed, Lost and Stolen Rights
                    Certificates............................................  28
Section 3.9      Persons Deemed Owners......................................  29
Section 3.10     Delivery and Cancellation of Certificates..................  30
Section 3.11     Agreement of Rights Holders................................  30






                                   Article IV
         ADJUSTMENTS TO THE RIGHTS IN THE EVENT OF CERTAIN TRANSACTION

Section 4.1      Flip-in....................................................  31
Section 4.2      Flip-over..................................................  35

                                  Article V
                                MISCELLANEOUS

Section 5.1      Redemption.................................................  36
Section 5.2      Expiration.................................................  37
Section 5.3      Issuance of New Rights Certificates........................  38
Section 5.4      Supplements and Amendments.................................  39
Section 5.5      Fractional Shares..........................................  39
Section 5.6      Rights of Action...........................................  39
Section 5.7      Rights Holder Not Deemed a Stockholder.....................  40
Section 5.8      Notice of Proposed Actions.................................  41
Section 5.9      Notices....................................................  41
Section 5.10     Suspension of Exercisability...............................  42
Section 5.11     Costs of Enforcement.......................................  43
Section 5.12     Successors.................................................  43
Section 5.13     Benefits of this Agreement.................................  43
Section 5.14     Determination and Actions by the Board of
                     Directors, etc.........................................  43
Section 5.15     Severability...............................................  45
Section 5.16     Governing Law..............................................  44
Section 5.17     Counterparts...............................................  44
Section 5.18     Descriptive Headings.......................................  44




                                       ii




                                    EXHIBITS

Exhibit A        Form of Rights Certificate (Together with Form of
                 Election to Exercise)

Exhibit B        Form of Articles Supplementary





                                      iii






                          STOCKHOLDER RIGHTS AGREEMENT
                          ----------------------------

         STOCKHOLDER  RIGHTS AGREEMENT (this "Agreement"),  dated as of April
23, 1997, between HCIA Inc., a Maryland corporation (the "Company"), and 
ChaseMellon Shareholder Services, as Rights Agent (the "Rights Agent," which 
term shall include any successor Rights Agent hereunder).

         The  Board of  Directors  of the  Company has  authorized  and declared
a dividend  of one right  ("Right")  in respect of each share of Common Stock
(as hereinafter defined) held of record as of the close of business on April 24,
1997 (the  "Record  Date") and has further  authorized  the  issuance of one
Right in respect of each share of Common  Stock issued after the Record Date and
prior to the  Separation  Date  (as  hereinafter  defined)  and,  to the  extent
provided in Section 5.3, each share of Common Stock issued after the  Separation
Date.  Each Right entitles the holder  thereof,  after the  Separation  Date, to
purchase  securities  of the Company  (or, in certain  cases,  of certain  other
entities) pursuant to the terms and subject to the conditions set forth herein.

         Accordingly,  in  consideration  of the premises and the respective
agreements set forth herein, the parties hereby agree as follows:






                                   ARTICLE I

                                  DEFINITIONS

         1.1 Definitions.  For  purposes of this  Agreement,  the  following
terms have the meanings indicated:

         "Acquiring  Person"  shall mean any Person who is a Beneficial
Owner  of 15% or more of the  outstanding  shares  of  Common  Stock;  provided,
however,  that the term "Acquiring  Person" shall not include any Person (i) who
is the Beneficial Owner of 15% or more of the outstanding shares of Common Stock
on the date of this Agreement or who shall become the Beneficial Owner of 15% or
more of the  outstanding  shares  of  Common  Stock  solely  as a  result  of an
acquisition by the Company of shares of Common Stock,  until such time hereafter
or thereafter as any of such Persons  shall become the  Beneficial  Owner (other
than by means of a stock  dividend or stock split) of any  additional  shares of
Common Stock, (ii) who is the Beneficial Owner of 15% or more of the outstanding
shares of Common Stock but who acquired Beneficial Ownership of shares of Common
Stock without any plan or intention to seek or affect control of the Company, if
such Person promptly enters into an irrevocable  commitment  promptly to divest,
and  thereafter  promptly  divests  (without  exercising or retaining any power,
including  voting,  with respect to such  shares),  sufficient  shares of Common
Stock (or securities  convertible  into,  exchangeable  into or exercisable  for
Common  Stock) so that such Person ceases to be the  Beneficial  Owner of 15% or
more of the outstanding  shares of Common Stock or (iii) who  Beneficially  Owns
shares of


                                       2



Common Stock consisting  solely of one or more of (A) shares of Common Stock
Beneficially Owned pursuant to the grant or exercise of an option granted to
such Person by the Company in connection  with an agreement to merge with, or
acquire,  the Company entered into prior to a Flip-in Date, (B) shares of Common
Stock (or securities  convertible  into,  exchangeable  into or exercisable  for
Common Stock)  Beneficially Owned by such Person or its Affiliates or Associates
at the time of grant of such option,  (C) shares of Common Stock (or  securities
convertible into, exchangeable into or exercisable for Common Stock) acquired by
Affiliates or  Associates of such Person after the time of such grant which,  in
the aggregate,  amount to less than 1% of the outstanding shares of Common Stock
and (D) shares of Common Stock (or  securities  convertible  into,  exchangeable
into or  exercisable  for Common  Stock)  which are held by such Person in trust
accounts,  managed  accounts  and the  like  or  otherwise  held in a  fiduciary
capacity, that are beneficially owned by third persons who are not Affiliates or
Associates  of such  Person or  acting  together  with such  Person to hold such
shares,  or which  are  held by such  Person  in  respect  of a debt  previously
contracted. In addition, the Company, any wholly-owned Subsidiary of the Company
and any employee stock  ownership or other employee  benefit plan of the Company
or a wholly-owned Subsidiary of the Company shall not be an Acquiring Person.

         "Affiliate" and  "Associate"  shall have the respective  meanings
ascribed to such terms in Rule 12b-2 under the  Securities  Exchange Act of
1934, as amended (the  "Exchange  Act"),  as such Rule is in effect on the date
of this Agreement.


                                       3




         A Person shall be deemed to be the "Beneficial  Owner," and to have
"Beneficial  Ownership" of, and to "Beneficially Own," any securities as to
which such Person or any of such Person's  Affiliates or Associates is or may be
deemed to be the beneficial  owner of pursuant to Rule 13d-3 and 13d-5 under the
Exchange Act, as such Rules are in effect on the date of this Agreement, as well
as any securities as to which such Person or any of such Person's  Affiliates or
Associates  has the right to become  Beneficial  Owner  (whether  such  right is
exercisable  immediately  or only after the passage of time or the occurrence of
conditions) pursuant to any agreement, arrangement or understanding, or upon the
exercise of conversion rights,  exchange rights, rights (other than the Rights),
warrants or options, or otherwise; provided, however, that a Person shall not be
deemed to be the "Beneficial Owner," or to have "Beneficial Ownership" of, or to
"Beneficially  Own," any  security  (i) solely  because  such  security has been
tendered  pursuant to a tender or  exchange  offer made by such Person or any of
such Person's  Affiliates or Associates until such tendered security is accepted
for  payment or  exchange  or (ii)  solely  because  such  Person or any of such
Person's  Affiliates or Associates has or shares the power to vote or direct the
voting of such  security  pursuant to a  revocable  proxy given in response to a
public proxy or consent  solicitation made to more than ten holders of shares of
a class of stock of the Company  registered under Section 12 of the Exchange Act
and pursuant to, and in accordance  with, the applicable  rules and  regulations
under the  Exchange  Act,  except if such  power (or the  arrangements  relating
thereto) is then reportable  under Item 6 of Schedule 13D



                                       4



under the Exchange Act (or any similar provision of a comparable or successor
report).  Notwithstanding the  foregoing,  no  officer  or  director  of the
Company  shall be  deemed to Beneficially  Own any  securities  of any other
Person by virtue of any actions such officer or director takes in such capacity.
For purposes of this Agreement, in  determining  the percentage of the
outstanding  shares of Common Stock with respect to which a Person is the
Beneficial  Owner,  all shares as to which such Person is deemed the Beneficial
Owner shall be deemed outstanding.

         "Business  Day"  shall  mean any day other  than a  Saturday,  Sunday
or a day on which  banking institutions in Baltimore, Maryland are generally
authorized or obligated by law or executive order to close.

         "Close of  Business"  on any given  date shall mean 5:00 p.m.
Baltimore,  Maryland  time on such date (or, if such date is not a Business Day,
5:00 p.m.  Baltimore,  Maryland time on the next succeeding  Business Day).

         "Common Stock" shall mean the shares of Common Stock, par value $0.01
per share, of the Company.

         "Disinterested  Director"  shall mean any member of the Board of
Directors of the Company,  while such Person is a member of the board, who is
not (i) an Acquiring  Person, or an Affiliate  or  Associate  of an  Acquiring
Person,  or a  representative  of an Acquiring Person or of any such Affiliate
or Associate,  or (ii) a Person, or an Affiliate,  Associate,  or representative
of a Person, any of whom has stated



                                       5



an intent to take,  or to consider  taking, any action  which would result in
such Person  becoming  an  Acquiring   Person, or  which  would  cause  a
Flip-over Transaction or Event.

         "Exchange  Date" shall mean the time at which the right to exercise
the Rights  shall  terminate pursuant to Section 4.1(c) hereof.

         "Exercise  Price"  shall  mean,  as of any date,  the price at which a
holder  may  purchase  the securities  issuable  upon  exercise of one whole
Right.  Until  adjustment  thereof in  accordance  with the terms hereof, the
Exercise Price shall equal $240.

         "Expiration  Date" shall mean the earliest of (i) the Exchange Date,
(ii) the  Redemption  Date, (iii) April 22, 2007 or (iv) upon the merger of the
Company  into  another  corporation  pursuant to an  agreement entered into
prior to a Flip-in Date.

         "Flip-in  Date"  shall  mean the tenth  business  day after  any Stock
Acquisition  Date or such earlier or later date as the Board of  Directors  of
the  Company may from time to time fix by  resolution  adopted prior to the
Flip-in Date that would otherwise have occurred.

         "Flip-over  Entity",  for purposes of Section 4.2,  shall mean
(x) in the case of a Flip-over  Transaction or Event  described in clause (i) of
the definition  thereof,  the Person issuing any securities into which shares of
Common Stock are being  converted or exchanged  and, if no such  securities  are
being issued, the other party to such Flip-over  Transaction or Event and (y) in
the case of a Flip-over  Transaction  or Event referred to in clause (ii) of the
definition  thereof,  the Person receiving the greatest portion of the assets or
earning power being transferred in such Flip-over Transaction




                                       6



or Event, provided in all  cases if such  Person  is a  subsidiary  of a
corporation,  the  parent corporation shall be the Flip-over Entity.

         "Flip-over  Stock" shall mean the capital stock (or similar  equity
interest)  with the greatest voting power in respect of the election of
directors (or other persons  similarly  responsible for direction of the
business and affairs) of the Flip-over Entity.

         "Flip-over  Transaction  or Event" shall mean a transaction or series
of  transactions  after a Flip-in Date in which,  directly or indirectly, (i)
the Company shall  consolidate  or merge or  participate in a share exchange
with any  other  Person  if, at the time of the  consolidation,  merger or share
exchange or at the time the Company  enters into any  agreement  with respect to
any such consolidation,  merger or share exchange, the Acquiring Person Controls
the Board of Directors of the Company and either (A) any term of or  arrangement
concerning  the  treatment  of shares of  capital  stock in such  consolidation,
merger or share  exchange  relating to the Acquiring  Person is not identical to
the terms and arrangements  relating to other holders of the Common Stock or (B)
the Person with whom the  transaction  or series of  transactions  occurs is the
Acquiring  Person or an Affiliate or Associate of the  Acquiring  Person or (ii)
the Company shall sell or otherwise transfer (or one or more of its Subsidiaries
shall sell or otherwise  transfer)  assets (A) aggregating  more than 50% of the
assets  (measured by either book value or fair market  value) or (B)  generating
more  than 50% of the  operating  income  or cash  flow of the  Company  and its
Subsidiaries  (taken as a whole) to any Person (other than the Company or one or
more of its wholly owned


                                       7




Subsidiaries) or to two or more such Persons which are Affiliates or Associates
or otherwise acting in concert,  if, at the time of the entry by the Company (or
any such  Subsidiary) into an agreement with respect to such sale or transfer of
assets,  the  Acquiring  Person  Controls  the Board of Directors  of the
Company.  An  Acquiring  Person shall be deemed to Control the Company's  Board
of Directors  when,  following a Flip-in Date,  the persons who were  directors
of the Company before the Flip-in Date shall cease to constitute a majority of
the Company's Board of Directors.

         "Market  Price" per share of any  securities on any date shall mean the
average  of the daily  closing  prices  per  share of such  securities
(determined  as  described  below) on each of the 20  consecutive  Trading  Days
through and including the Trading Day immediately preceding such date; provided,
however,  that if an event of a type analogous to any of the events described in
Section 3.4 hereof shall have caused the closing  prices used to  determine  the
Market Price on any Trading Days during such period of 20 Trading Days not to be
fully comparable with the closing price on such date, each such closing price so
used shall be  appropriately  adjusted in order to make it fully comparable with
the closing price on such date. The closing price per share of any securities on
any date shall be the last reported sale price,  or, in case no sale takes place
or is quoted on such date,  the average of the closing bid and asked  prices for
each share of such securities, in either case as reported by the Nasdaq National
Market or, if the securities are not quoted on the Nasdaq  National  Market,  as
reported in the principal consolidated transaction reporting system with respect
to securities listed on the


                                       8




principal national  securities exchange on which the securities  are listed or
admitted  to trading  or, if the  securities  are not listed or admitted to
trading on any  national  securities  exchange or national market system,  as
reported by the National  Association of Securities  Dealers, Inc. Automated
Quotation System or such other system then in use, or, if on any such date the
securities  are not listed or admitted to trading on any national securities
exchange or national market system or quoted by any such organization, the
average of the closing bid and asked prices as furnished by a professional
market  maker  making a market in the  securities  selected by the Board of
Directors of the Company;  provided,  however, that if on any such date the
securities  are not listed or admitted to trading on a national  securities
exchange or national market system or traded in the over-the-counter market, the
closing  price per share of such  securities  on such date  shall  mean the fair
value per share of  securities  on such date as  determined in good faith by the
Board  of  Directors  of the  Company,  after  consultation  with  a  nationally
recognized  investment banking firm, and set forth in a certificate delivered to
the Rights Agent.

         "Person" shall mean any individual, firm, partnership, association,
group (as such term is used in Rule 13d-5 under the Exchange  Act, as such Rule
is in effect on the date of this  Agreement),  corporation or other entity, and
shall include any successor (by merger or otherwise) of such entity.



                                       9



         "Preferred  Stock" shall mean the series of Class A Preferred  Stock,
par value $0.01 per share, of the  Company  created  by  Articles  Supplementary
in  substantially  the form set  forth in  Exhibit  B hereto appropriately
completed.

         "Redemption Price" shall mean an amount equal to $0.01.

         "Redemption  Date" shall mean the time at which the right to exercise
the Rights shall  terminate pursuant to Section 5.1 hereof.

         "Separation  Date"  shall  mean the close of  business  on the earlier
of (i) the  tenth  business  day (or such  later  date as the  Board of
Directors of the Company may from time to time fix by  resolution  adopted prior
to the Separation  Date that would  otherwise  have occurred)  after the date on
which any Person  commences a tender or exchange  offer which,  if  consummated,
would result in such Person's  becoming an Acquiring Person and (ii) the Flip-in
Date; provided, that if the foregoing results in the Separation Date being prior
to the Record Date,  the  Separation  Date shall be the Record Date and provided
further,  that if any tender or exchange offer referred to in clause (i) of this
paragraph  is  cancelled,   terminated  or  otherwise  withdrawn  prior  to  the
Separation  Date  without the  purchase of any shares of Common  Stock  pursuant
thereto,  such offer shall be deemed,  for purposes of this paragraph,  never to
have been made.

         "Stock  Acquisition Date" shall mean the day of the first public
announcement by the Company (by any means) that an Acquiring Person has become
such.


                                       10



         "Subsidiary"  of any  specified  Person  shall mean any  corporation or
other  entity of which a majority of the voting power of the equity securities
or a majority of the equity interest is Beneficially  Owned, directly or
indirectly, by such Person.

         "Trading Day," when used with respect to any securities, shall mean a
day on  which  the  New  York  Stock  Exchange, Inc.  is  open  for  the
transaction  of business  or, if such  securities  are not listed or admitted to
trading  on the New York  Stock  Exchange,  Inc.,  a day on which the  principal
national  securities exchange on which such securities are listed or admitted to
trading is open for the  transaction of business or, if such  securities are not
listed or admitted to trading on any national  securities  exchange,  a Business
Day.

                                   ARTICLE II

                                THE RIGHTS AGENT

                  2.1 General.  (a) The Company hereby appoints the Rights Agent
to act as agent for the  Company  in  accordance  with the terms and  conditions
hereof, and the Rights Agent hereby accepts such appointment. The Company agrees
to pay to the Rights Agent reasonable  compensation for all services rendered by
it  hereunder  and,  from  time to time,  on  demand of the  Rights  Agent,  its
reasonable  expenses  and counsel fees and other  disbursements  incurred in the
administration  and execution of this Agreement and the exercise and performance
of its duties  hereunder.  The Company also agrees to indemnify the Rights Agent
for, and to hold it harmless against, any loss, liability, or expense,  incurred
without  negligence,  bad faith or willful  misconduct on the



                                       11

part of the Rights Agent, for anything done or omitted to be done by the Rights
Agent in connection with the acceptance and  administration  of this Agreement,
including the costs and expenses of defending against any claim of liability.

                  (b) The Rights  Agent  shall be  protected  and shall incur no
liability  for or in respect of any action  taken,  suffered or omitted by it in
connection  with its  administration  of this  Agreement  in  reliance  upon any
certificate  for  securities   purchasable  upon  exercise  of  Rights,   Rights
Certificate,  certificate  for other  securities  of the Company,  instrument of
assignment  or transfer,  power of  attorney,  endorsement,  affidavit,  letter,
notice, direction, consent,  certificate,  statement, or other paper or document
believed by it to be genuine and to be signed,  executed and,  where  necessary,
verified or acknowledged, by the proper person or persons.

                  2.2 Merger or Consolidation or Change of Name of Rights Agent.
(a) Any  corporation  into which the Rights Agent or any successor  Rights Agent
may be merged or with which it may be consolidated, or any corporation resulting
from any  merger or  consolidation  to which the Rights  Agent or any  successor
Rights  Agent is a  party,  or any  corporation  succeeding  to the  shareholder
services  business of the Rights Agent or any successor  Rights Agent,  shall be
the successor to the Rights Agent under this Agreement  without the execution or
filing of any paper or any further act on the part of any of the parties hereto,
provided that such corporation  would be eligible for appointment as a successor
Rights  Agent under the  provisions  of Section 2.4 hereof.  In case at the time
such successor Rights Agent succeeds to the agency created by this



                                       12





Agreement any of the Rights  Certificates have been countersigned but not
delivered,  any such successor Rights Agent may adopt the  countersignature of
the predecessor Rights Agent and deliver such Rights Certificates so
countersigned; and in case at that time any of the Rights Certificates have not
been  countersigned,  any successor Rights Agent may countersign such Rights
Certificates either in the name of the predecessor  Rights Agent or in the name
of the successor  Rights Agent;  and in all such cases such Rights Certificates
will have the full force provided in the Rights Certificates and in this
Agreement.

                  (b) In case  at any  time  the  name of the  Rights  Agent  is
changed  and at  such  time  any of the  Rights  Certificates  shall  have  been
countersigned but not delivered, the Rights Agent may adopt the countersignature
under its prior name and deliver Rights  Certificates so  countersigned;  and in
case  at  that  time  any  of  the  Rights  Certificates  shall  not  have  been
countersigned,  the Rights Agent may countersign such Rights Certificates either
in its prior name or in its  changed  name;  and in all such  cases such  Rights
Certificates  shall have the full force provided in the Rights  Certificates and
in this Agreement.

                  2.3 Duties of Rights Agent.  The Rights Agent  undertakes the
duties and  obligations  imposed by this Agreement upon the following  terms and
conditions,  by all of which the Company and the holders of Rights Certificates,
by their acceptance thereof, shall be bound:



                                       13



                  (a) The Rights Agent may consult  with legal  counsel (who may
be legal counsel for the Company), and the opinion of such counsel will be full
and complete  authorization  and protection to the Rights Agent as to any action
taken or omitted by it in good faith and in accordance with such opinion.

                  (b) Whenever  in the  performance of its  duties  under this
Agreement  the Rights Agent deems it  necessary  or desirable  that any fact or
matter be proved or  established by the Company prior to taking or suffering any
action hereunder,  such fact or matter (unless other evidence in respect thereof
be herein  specifically  prescribed) may be deemed to be conclusively proved and
established by a certificate  signed by a person believed by the Rights Agent to
be the Chairman of the Board,  the President or any Senior Vice President or the
Secretary or any Assistant Secretary of the Company and delivered to the Rights
Agent; and such certificate will be full  authorization to the Rights Agent for
any action taken or suffered in good faith by it under the  provisions  of this
Agreement in reliance upon such certificate.

                  (c) The Rights  Agent will be liable hereunder  only for its
own  negligence,  bad faith or willful misconduct.

                  (d) The  Rights  Agent  will not be liable for or by reason of
any of the statements of fact or recitals  contained in this Agreement or in the
certificates  for securities  purchasable  upon exercise of Rights or the Rights
Certificates (except its countersignature  thereof) or be required to verify the
same,  but all such  statements and recitals are and will be deemed to have been
made by the Company only.



                                       14


                  (e) The Rights Agent will not be under any  responsibility  in
respect of the validity of this  Agreement or the execution and delivery  hereof
(except  the due  authorization,  execution  and  delivery  hereof by the Rights
Agent) or in  respect  of the  validity  or  execution  of any  certificate  for
securities purchasable upon exercise of Rights or Rights Certificate (except its
countersignature  thereof);  nor will it be  responsible  for any  breach by the
Company of any  covenant or  condition  contained  in this  Agreement  or in any
Rights  Certificate;   nor  will  it  be  responsible  for  any  change  in  the
exercisability  of the Rights  (including  the Rights  becoming void pursuant to
Section  4.1(b)  hereof) or any  adjustment  required  under the  provisions  of
Section 3.4, 4.1 or 4.2 hereof or responsible  for the manner,  method or amount
of any such adjustment or the  ascertaining of the existence of facts that would
require any such adjustment (except with respect to the exercise of Rights after
receipt of the  certificate  contemplated  by Section  3.4  describing  any such
adjustment);   nor  will  it  by  any  act  hereunder  be  deemed  to  make  any
representation  or  warranty  as to  the  authorization  of  any  Rights  or the
reservation  of any  securities  purchasable  upon exercise of Rights,  or as to
whether any securities purchasable upon exercise of Rights will, when issued, be
duly and validly authorized,  executed,  issued and delivered and fully paid and
nonassessable.

                  (f) The  Company  agrees  that  it  will  perform,   execute,
acknowledge  and deliver or cause to be performed,  executed,  acknowledged  and
delivered  all such further and other acts,  instruments  and  assurances as may
reasonably be required by




                                       15




the Rights Agent for the carrying out or performing by the Rights Agent of the
provisions of this Agreement.

                  (g) The Rights  Agent is hereby  authorized  and  directed  to
accept instructions with respect to the performance of its duties hereunder from
any person  believed by the Rights Agent to be the  Chairman of the Board,  the
President  or any  Senior  Vice President  or the  Secretary  or any  Assistant
Secretary  of  the  Company, and  to  apply  to  such  persons  for  advice  or
instructions in connection with its duties,  and it shall not be liable for any
action taken or suffered by it in good faith in accordance with  instructions of
any such person.

                  (h) The Rights Agent and any stockholder, director, officer or
employee of the Rights Agent may buy,  sell or deal in Common  Stock,  Rights or
other securities of the Company or become interested in any transaction in which
the Company may be interested,  or contract with or lend money to the Company or
otherwise  act as fully and freely as though it were not Rights Agent under this
Agreement. Nothing  herein  shall  preclude the Rights Agent from acting in any
other capacity for the Company or for any other legal entity.

                  (i) The  Rights  Agent may  execute  and  exercise  any of the
rights or powers hereby vested in it or perform any duty hereunder either itself
or by or  through  its  attorneys  or agents,  and the Rights  Agent will not be
answerable or  accountable  for any act,  default,  neglect or misconduct of any
such attorneys or agents or for any loss to



                                       16



the Company  resulting from any such act, default,  neglect or misconduct,
provided reasonable care was exercised in the selection and continued employment
thereof.

                  2.4 Change of Rights Agent. The Rights Agent may resign and be
discharged  from its duties under this  Agreement  upon 90 days' notice (or such
lesser notice as is acceptable to the Company) in writing mailed to the Company
and to the transfer agent for the Common Stock by registered or certified  mail,
and to the holders of the Rights in accordance with Section 5.9. The Company may
remove the Rights  Agent upon 30 days'  notice in writing,  mailed to the Rights
Agent and to the transfer  agent for the Common Stock by registered or certified
mail,  and to the holders of the Rights in  accordance  with Section 5.9. If the
Rights  Agent  should  resign or be removed or  otherwise  become  incapable  of
acting, the Company will appoint a successor to the Rights Agent. If the Company
fails to make such appointment within a period of 30 days after such removal or
after it has been notified in writing of such  resignation  or incapacity by the
resigning or  incapacitated Rights Agent or by the holder of any Rights  (which
holder shall,  with such notice,  submit such holder's  Rights  Certificate  for
inspection by the Company), then the holder of any Rights may apply to any court
of  competent jurisdiction  for the  appointment  of a new  Rights  Agent.  Any
successor Rights  Agent,  whether  appointed by the Company or by such a court,
shall be a corporation organized and doing business under the laws of the United
States or of the State of Maryland or any other State of the United  States,  in
good standing, which is authorized under such laws to exercise the powers of the
Rights Agent  contemplated  by



                                       17

this  Agreement and is subject to  supervision or examination  by  federal  or
state  authority  and  which has at the time of its appointment  as  Rights
Agent  a  combined  capital  and  surplus  of at  least $50,000,000.  After
appointment,  the successor Rights Agent will be vested with the  same  powers,
rights,  duties  and  responsibilities  as  if it  had  been originally  named
as  Rights  Agent  without  further  act  or  deed;  but  the predecessor
Rights  Agent shall  deliver and transfer to the  successor  Rights Agent any
property at the time held by it hereunder, and execute and deliver any further
assurance,  conveyance, act or deed necessary for the purpose. Not later than
the effective  date of any such  appointment,  the Company will file notice
thereof in writing with the predecessor  Rights Agent and each transfer agent of
the Common  Stock,  and mail a notice  thereof in writing to the  holders of the
Rights. Failure to give any notice provided for in this Section 4.4, however, or
any defect therein, shall not affect the legality or validity of the resignation
or removal of the Rights Agent or the appointment of the successor Rights Agent,
as the case may be.

                                  ARTICLE III

                                   THE RIGHTS

                  3.1 Summary of Rights. As soon as practicable after the Record
Date, the Company will mail a letter summarizing the terms of the Rights to each
holder of record of Common Stock as of the Record Date, at such holder's address
as shown by the records of the Company.


                                       18



                  3.2 Legend on Common Stock Certificates.  Certificates for the
Common Stock issued after the Record Date but prior to the Separation Date shall
evidence one Right for each share of Common Stock represented  thereby and shall
have impressed  on,  printed on,  written on or  otherwise  affixed to them the
following legend:

                  Until the Separation Date (as defined in the Rights  Agreement
                  referred  to  below),  this  certificate  also  evidences  and
                  entitles the holder hereof to certain Rights as set forth in a
                  Rights  Agreement,  dated as of April 30, 1997 (as such may be
                  amended from time to time,  the "Rights Agreement"),  between
                  HCIA Inc.  (the  "Company")  and Chemical  Mellon Shareholder
                  Services,  as Rights  Agent,  the  terms of which  are  hereby
                  incorporated  herein  by  reference  and a copy of which is on
                  file at the principal executive offices of the Company.  Under
                  certain  circumstances,  as set forth in the Rights Agreement,
                  such  Rights  may be  redeemed,  may  become exercisable  for
                  securities or assets of the Company or of another entity,  may
                  be exchanged for shares of Common Stock or other securities or
                  assets of the Company,  may expire,  may become void (if they
                  are  "Beneficially  Owned"  by an  "Acquiring  Person"  or an
                  Affiliate or Associate  thereof,  as such terms are defined in
                  the  Rights  Agreement,  or by  any  transferee  of any of the
                  foregoing)  or may be evidenced by separate  certificates  and
                  may no longer be evidenced by this  certificate.  The Company
                  will mail or arrange  for the mailing of a copy of the Rights
                  Agreement  to the holder of this  certificate without  charge
                  promptly after the receipt of a written request therefor.

Certificates representing shares of Common Stock that are issued and outstanding
at the Record  Date  shall  evidence  one Right for each  share of Common  Stock
evidenced thereby notwithstanding the absence of the foregoing legend.

                  3.3 Exercise of Rights: Separation of Rights.

                  (a) Subject  to  Sections  4.1,  5.1 and 5.10 and  subject  to
adjustment  as herein set forth,  each Right will  entitle  the holder  thereof,
after the Separation Date and


                                       19



prior to the Expiration Date, to purchase, for the Exercise Price, one one-
hundredth of a share of Preferred Stock.

                  (b) Until the  Separation  Date, (i) no Right may be exercised
and (ii) each Right will be  evidenced  by the  certificate  for the  associated
share of Common Stock (together, in the case of certificates issued prior to the
Record Date,  with the letter  mailed to the record holder  thereof  pursuant to
Section  3.1)  and  will  be  transferable  only  together  with,  and  will  be
transferred  by a  transfer  (whether  with or without  such  letter)  of,  such
associated share.

                  (c) Subject to this  Section 3.3 and to Sections  4.1, 5.1 and
5.10, after the Separation Date and prior to the Expiration Date, the Rights (i)
may be exercised  and (ii) may be  transferred  independent  of shares of Common
Stock.  Promptly  following the  Separation  Date, the Rights Agent will mail to
each holder of record of Common Stock as of the Separation  Date (other than any
Person  whose  Rights  have become void  pursuant  to Section  4.1(b)),  at such
holder's  address as shown by the records of the  Company  (the  Company  hereby
agreeing  to  furnish  copies  of such  records  to the  Rights  Agent  for this
purpose),  (x) a certificate (a "Rights  Certificate") in substantially the form
of Exhibit A hereto appropriately  completed,  representing the number of Rights
held  by  such  holder  at  the  Separation   Date  and  having  such  marks  of
identification  or  designation  and such  legends,  summaries  or  endorsements
printed thereon as the Company may deem  appropriate and as are not inconsistent
with the provisions of this Agreement,  or as may be required to comply with any
law or with any rule or



                                       20




regulation  made  pursuant  thereto or  with  any  rule  or regulation  of  any
national  securities exchange or quotation system on which the Rights  may from
time to time be listed or traded,  or to conform to usage,  and (y) a disclosure
statement describing the Rights.

                  (d)  Subject  to  Sections  4.1,  5.1 and 5.10,  Rights may be
exercised  on any  Business  Day  after  the  Separation  Date and  prior to the
Expiration  Date by  submitting  to the  Rights  Agent  the  Rights  Certificate
evidencing  such Rights with an Election to Exercise (an "Election to Exercise")
substantially  in the form attached to the Rights  Certificate  duly  completed,
accompanied  by payment in cash, or by certified or official bank check or money
order payable to the order of the Company,  of a sum equal to the Exercise Price
multiplied by the number of Rights being exercised and a sum sufficient to cover
any  transfer  tax or charge  which may be payable  in  respect of any  transfer
involved in the transfer or delivery of Rights  Certificates  or the issuance or
delivery of certificates  for shares or depositary  receipts (or both) in a name
other than that of the holder of the Rights being exercised.

                  (e) Upon receipt of a Rights Certificate,  with an Election to
Exercise  accompanied by payment as set forth in Section 3.3(d),  and subject to
Sections  4.1, 5.1 and 5.10,  the Rights Agent will  thereupon  promptly  (i)(A)
request stock certificates  evidencing such number of shares or other securities
to be purchased (the Company hereby  irrevocably  authorizing its transfer agent
to comply with all such  requisitions) and (B) if the Company elects pursuant to
Section 5.5 not to issue certificates



                                       21




representing  fractional shares,  request depositary  receipts  representing
the  fractional  shares to be  purchased  or request the amount of cash to be
paid in lieu of fractional shares in accordance with  Section  5.5 and  (ii)
after  receipt  of such  certificates,  depositary receipts  and/or cash,
deliver the same to or upon the order of the  registered holder of such Rights
Certificate,  registered (in the case of  certificates or depositary receipts)
in such name or names as may be designated by such holder.

                  (f) In case the holder of any Rights shall  exercise less than
all the Rights  evidenced  by such  holder's  Rights  Certificate,  a new Rights
Certificate  evidencing the Rights  remaining  unexercised will be issued by the
Rights Agent to such holder or to such holder's duly authorized assigns.

                  (g) The Company covenants and agrees that it will (i) take all
such  action  as may be  necessary  to ensure  that all  shares  delivered  upon
exercise of Rights shall, at the time of delivery of the  certificates  for such
shares  (subject  to  payment  of the  Exercise  Price),  be  duly  and  validly
authorized,  executed,  issued and delivered  and fully paid and  nonassessable;
(ii) take all such  action as may be  necessary  to comply  with any  applicable
requirements  of the Securities  Act of 1933 or the  Securities  Exchange Act of
1934, and the rules and regulations  thereunder,  and any other  applicable law,
rule or regulation,  in connection with the issuance of any shares upon exercise
of Rights;  and (iii) pay when due and  payable  any and all  federal  and state
transfer  taxes and  charges  which may be payable  in  respect of the  original
issuance or delivery of the Rights Certificates or of any shares issued upon the
exercise of Rights,


                                       22



provided  that the Company shall not be required to pay any transfer tax or
charge which may be payable in respect of any transfer  involved in the transfer
or delivery of Rights  Certificates  or the issuance or delivery of certificates
for shares in a name other than that of the holder of the Rights being
transferred or exercised.

                  3.4  Adjustments to Exercise Price;  Number of Rights.  (a) In
the event the  Company  shall at any time after the Record Date and prior to the
Separation  Date (i) declare or pay a dividend on Common Stock payable in Common
Stock,  (ii)  subdivide  the  outstanding  Common  Stock  or (iii)  combine  the
outstanding  Common Stock into a smaller  number of shares of Common Stock,  (x)
the Exercise Price in effect after such adjustment will be equal to the Exercise
Price in effect  immediately  prior to such adjustment  divided by the number of
shares of Common Stock (the  "Adjustment  Factor") that a holder of one share of
Common Stock  immediately  prior to such  dividend,  subdivision  or combination
would hold  thereafter as a result thereof and (y) each Right held prior to such
adjustment will become that number of Rights equal to the Adjustment Factor, and
the adjusted number of Rights will be deemed to be distributed  among the shares
of Common Stock with respect to which the original  Rights were  associated  (if
they  remain  outstanding)  and the shares  issued in respect of such  dividend,
subdivision  or  combination,  so that each such share of Common Stock will have
exactly one Right  associated  with it. Each  adjustment  made  pursuant to this
paragraph  shall be made as of the payment or effective  date for the applicable
dividend, subdivision or combination.




                                       23



                  In the event the  Company  shall at any time  after the Record
Date and prior to the Separation Date issue any shares of Common Stock otherwise
than in a transaction referred to in the preceding paragraph, each such share of
Common Stock so issued shall  automatically  have one new Right  associated with
it, which Right shall be evidenced by the certificate  representing  such share.
To the extent  provided in Section 5.3, Rights shall be issued by the Company in
respect of shares of Common  Stock that are issued or sold by the Company  after
the Separation Date.

                  (b) In the  event  the  Company  shall at any time  after  the
Record Date and prior to the Separation  Date issue or distribute any securities
or assets in respect of, in lieu of or in exchange  for Common Stock (other than
pursuant to a regular periodic cash dividend or a dividend paid solely in Common
Stock) whether by dividend, in a reclassification or recapitalization (including
any such transaction  involving a merger,  consolidation or share exchange),  or
otherwise,  the Company  shall make such  adjustments,  if any, in the  Exercise
Price,  number of Rights and/or  securities or other property  purchasable  upon
exercise  of  Rights  as the  Board of  Directors  of the  Company,  in its sole
discretion,  may deem to be  appropriate  under  the  circumstances  in order to
adequately  protect the  interests of the holders of Rights  generally,  and the
Company and the Rights Agent shall amend this  Agreement as necessary to provide
for such adjustments.

                  (c) Each  adjustment  to the Exercise  Price made  pursuant to
this Section 3.4 shall be calculated to the nearest cent. Whenever an adjustment
to the Exercise  Price



                                       24



is made  pursuant to this Section 3.4, the Company  shall promptly (i) prepare a
certificate  setting forth such  adjustment  and a brief statement of the facts
accounting  for such  adjustment  and (ii) file with the Rights  Agent and with
the  transfer  agent for the Common  Stock a copy of such certificate.

                  (d)  Rights   certificates   shall  represent  the  securities
purchasable  under the terms of this  Agreement,  including  any  adjustment  or
change in the securities  purchasable  upon exercise of the Rights,  even though
such certificates may continue to express the securities purchasable at the time
of issuance of the initial Rights Certificates.

                  3.5 Date on Which Exercise is Effective.  Each person in whose
name any  certificate for shares is issued upon the exercise of Rights shall for
all  purposes  be  deemed to have  become  the  holder  of record of the  shares
represented  thereby on the date upon which the  Rights  Certificate  evidencing
such  Rights was duly  surrendered  and payment of the  Exercise  Price for such
Rights (and any applicable taxes and other  governmental  charges payable by the
exercising holder hereunder) was made;  provided,  however,  that if the date of
such  surrender and payment is a date upon which the stock transfer books of the
Company are closed, such person shall be deemed to have become the record holder
of such  shares on, and such  certificate  shall be dated,  the next  succeeding
Business Day on which the stock transfer books of the Company are open.



                                       25



                  3.6 Execution,  Authentication,  Delivery and Dating of Rights
Certificates.  (a) The Rights  Certificates  shall be  executed on behalf of the
Company by its  Chairman  of the  Board,  President  or one of its  Senior  Vice
Presidents,  under  its  corporate  seal  reproduced  thereon  attested  by  its
Secretary or one of its  Assistant  Secretaries.  The  signature of any of these
officers on the Rights Certificates may be manual or facsimile.

                  Rights Certificates bearing the manual or facsimile signatures
of  individuals  who were at any time the proper  officers of the Company  shall
bind the  Company,  notwithstanding  that such  individuals  or any of them have
ceased to hold such offices prior to the  countersignature  and delivery of such
Rights Certificates.

                  Promptly  after the  Separation  Date, the Company will notify
the Rights Agent of such  Separation  Date and will deliver Rights  Certificates
executed by the Company to the Rights Agent for  countersignature,  and, subject
to Section 4.1(b), the Rights Agent shall manually  countersign and deliver such
Rights  Certificates  to the holders of the Rights  pursuant  to Section  3.3(c)
hereof.  No Rights  Certificate  shall be valid for any purpose unless  manually
countersigned by the Rights Agent.

                  (b) Each Rights Certificate shall be dated the date of
countersignature thereof.

                  3.7 Registration,  Registration  of Transfer and Exchange.
(a) After the  Separation  Date, the Company will cause to be kept a register
(the "Rights  Register") in which, subject to such  reasonable  regulations as
it may  prescribe,  the Company will



                                       26




provide for the registration and transfer of Rights.  The Rights Agent is hereby
appointed "Rights  Registrar" for the purpose of maintaining the Rights Register
for the  Company  and  registering Rights  and  transfers  of Rights  after the
Separation  Date as herein provided.  In the event that the Rights  Agent shall
cease to be the  Rights Registrar,  the  Rights  Agent  will  have the right to
examine the Rights Register at all reasonable times after the Separation Date.

                  After the Separation  Date and prior to the  Expiration  Date,
upon  surrender  for   registration  of  transfer  or  exchange  of  any  Rights
Certificate,  and subject to the  provisions of this Section 3.7(c) and (d), the
Company will execute,  and the Rights Agent will countersign and deliver, in the
name of the holder or the  designated  transferee  or  transferees,  as required
pursuant  to the  holder's  instructions,  one or more new  Rights  Certificates
evidencing the same aggregate number of Rights as did the Rights  Certificate so
surrendered.

                  (b) Except as otherwise provided in Section 4.1(b), all Rights
issued upon any  registration  of  transfer  or exchange of Rights  Certificates
shall be the valid obligations of the Company, and such Rights shall be entitled
to the same benefits  under this Agreement as the Rights  surrendered  upon such
registration of transfer or exchange.

                  (c) Every Rights  Certificate  surrendered for registration of
transfer or exchange  shall be duly  endorsed,  or be  accompanied  by a written
instrument of transfer in form  satisfactory to the Company or the Rights Agent,
as the case  may be,  duly



                                       27



executed  by the  holder  thereof  or such  holder's attorney duly  authorized
in writing.  As a condition to the issuance of any new Rights  Certificate
under this Section 3.7, the Company may require the payment of a sum  sufficient
to cover any tax or other  governmental  charge that may be imposed in relation
thereto.

                  (d) The Company shall not be required to register the transfer
or  exchange of any Rights  after such  Rights  have  become void under  Section
4.1(b), been exchanged under Section 4.1(c) or been redeemed or terminated under
Section 5.1.

                  3.8 Mutilated, Destroyed, Lost and Stolen Rights Certificates.
(a) If any mutilated Rights Certificate is surrendered to the Rights Agent prior
to the Expiration  Date, then,  subject to Sections 4.1(b),  4.1(c) and 5.1, the
Company  shall  execute and the Rights  Agent shall  countersign  and deliver in
exchange therefor a new Rights Certificate  evidencing the same number of Rights
as did the Rights Certificate so surrendered.

                  (b) If there shall be  delivered to the Company and the Rights
Agent prior to the  Expiration  Date (i) evidence to their  satisfaction  of the
destruction,  loss or theft of any Rights  Certificate and (ii) such security or
indemnity  as may be  required  by them to hold  each of them  and any of  their
agents harmless,  then,  subject to Sections  4.1(b),  4.1(c) and 5.1 and in the
absence  of  notice  to the  Company  or  the  Rights  Agent  that  such  Rights
Certificate  has been  acquired  by a bona fide  purchaser,  the  Company  shall
execute and upon its request the Rights Agent shall countersign and deliver,  in
lieu of any such  destroyed,  lost or stolen  Rights  Certificate,  a new Rights
Certificate



                                       28



evidencing the same number of Rights as did the Rights  Certificate so
destroyed, lost or stolen.

                  (c)  As  a  condition  to  the  issuance  of  any  new  Rights
Certificate under this Section 3.8, the Company may require the payment of a sum
sufficient to cover any tax or other governmental  charge that may be imposed in
relation thereto and any other expenses  (including the fees and expenses of the
Rights Agent) connected therewith.

                  (d) Every  new  Rights  Certificate  issued  pursuant  to this
Section 3.8 in lieu of any destroyed,  lost or stolen Rights  Certificate  shall
evidence an original additional contractual  obligation of the Company,  whether
or not the  destroyed,  lost or stolen Rights  Certificate  shall be at any time
enforceable by anyone, and, subject to Section 4.1(b),  shall be entitled to all
the  benefits of this  Agreement  equally and  proportionately  with any and all
other Rights duly issued hereunder.

                  3.9  Persons  Deemed  Owners.  Prior to due  presentment  of a
Rights  Certificate  (or,  prior to the Separation  Date, the associated  Common
Stock certificate) for registration of transfer,  the Company,  the Rights Agent
and any agent of the  Company or the Rights  Agent may deem and treat the person
in whose name such Rights  Certificate  (or, prior to the Separation  Date, such
Common Stock certificate) is registered as the absolute owner thereof and of the
Rights evidenced thereby for all purposes  whatsoever,  including the payment of
the  Redemption  Price and neither  the  Company  nor the Rights  Agent shall be
affected by any notice to the contrary.  As used in this  Agreement,  unless the
context  otherwise  requires,  the term  "holder"  of any




                                       29



Rights  shall mean the registered  holder  of such  Rights  (or,  prior  to the
Separation  Date,  the associated shares of Common Stock).

                  3.10 Delivery and  Cancellation  of  Certificates.  All Rights
Certificates  surrendered  upon  exercise  or for  registration  of  transfer or
exchange  shall,  if surrendered  to any person other than the Rights Agent,  be
delivered to the Rights Agent and, in any case,  shall be promptly  cancelled by
the Rights  Agent.  The Company may at any time  deliver to the Rights Agent for
cancellation  any Rights  Certificates  previously  countersigned  and delivered
hereunder which the Company may have acquired in any manner whatsoever,  and all
Rights  Certificates  so  delivered  shall be promptly  cancelled  by the Rights
Agent. No Rights  Certificates  shall be countersigned in lieu of or in exchange
for any Rights  Certificates  cancelled as provided in this Section 3.10, except
as  expressly  permitted  by this  Agreement.  The Rights Agent shall return all
cancelled Rights Certificates to the Company.

                  3.11 Agreement  of Rights  Holders.  Every holder of Rights by
accepting  the same  consents and agrees with the Company and the Rights Agent
and with every other holder of Rights that:

                  (a)  prior  to  the  Separation   Date,  each  Right  will  be
transferable  only together  with, and will be transferred by a transfer of, the
associated share of Common Stock;

                  (b) after the Separation  Date, the Rights  Certificates  will
be  transferable  only on the Rights Register as provided herein;



                                       30





                  (c) prior to due  presentment  of a Rights  Certificate  (or,
prior to the  Separation  Date,  the associated  Common Stock  certificate)  for
registration  of transfer,  the  Company,  the Rights Agent and any agent of the
Company  or the  Rights  Agent may deem and treat the  person in whose  name the
Rights  Certificate  (or,  prior to the Separation  Date, the associated  Common
Stock certificate) is registered as the absolute owner thereof and of the Rights
evidenced thereby for all purposes  whatsoever,  and neither the Company nor the
Rights Agent shall be affected by any notice to the contrary;

                  (d) Rights  beneficially  owned by certain Persons will, under
the  circumstances  set forth in Section 4.1(b), become void; and

                  (e) this  Agreement  may be  supplemented  or amended from
time to time  pursuant to Section 3.4(b) or 5.4 hereof.

                                   ARTICLE IV

                          ADJUSTMENTS TO THE RIGHTS IN
                       THE EVENT OF CERTAIN TRANSACTIONS

                  4.1  Flip-in.  (a) In the event that  prior to the  Expiration
Date a Flip-in  Date shall occur,  except as provided in this Section 4.1,  each
Right shall  constitute  the right to purchase  from the Company,  upon exercise
thereof in accordance with the terms hereof (but subject to Section 5.10),  that
number of shares of Common Stock  having an aggregate  Market Price on the Stock
Acquisition  Date equal to twice the Exercise  Price for an amount in cash equal
to the  Exercise  Price  (such  right to be



                                       31



appropriately  adjusted in order to protect the interests of the holders of
Rights generally in the event that on or after such Stock  Acquisition  Date an
event of a type  analogous  to any of the events  described in Section  3.4(a)
or (b) shall have  occurred with respect to the Common Stock).

                  (b) Notwithstanding the foregoing, any Rights that are or were
Beneficially Owned on or after the Stock Acquisition Date by an Acquiring Person
or an Affiliate or Associate  thereof or by any transferee,  direct or indirect,
of any of the  foregoing  shall  become  void  and any  holder  of  such  Rights
(including  transferees)  shall thereafter have no right to exercise or transfer
such Rights under any provision of this Agreement.  If any Rights Certificate is
presented for assignment or exercise and the Person presenting the same will not
complete the  certification  set forth at the end of the form of  assignment  or
notice of election  to exercise  and  provide  such  additional  evidence of the
identity of the  Beneficial  Owner and its  Affiliates and Associates (or former
Beneficial  Owners and their  Affiliates  and  Associates)  as the Company shall
reasonably request,  then the Company shall be entitled conclusively to deem the
Beneficial  Owner thereof to be an Acquiring Person or an Affiliate or Associate
thereof or a transferee of any of the foregoing  and  accordingly  will deem the
Rights evidenced thereby to be void and not transferable or exercisable.

                  (c) The Board of  Directors of the Company may, at its option,
at any time after a Flip-in Date and prior to the time that an Acquiring  Person
becomes  the  Beneficial  Owner of more  than 50% of the  outstanding  shares of
Common  Stock,  elect  to



                                       32



exchange  all (but  not  less  than  all) of the then outstanding  Rights
(which  shall not  include  Rights  that have  become  void pursuant to the
provisions of Section  4.1(b)) for shares of Common Stock at an exchange ratio
of one share of Common Stock per Right, appropriately adjusted in order to
protect the interests of holders of Rights  generally in the event that after
the  Separation  Date an event of a type  analogous  to any of the  events
described  in Section  3.4(a) or (b) shall  have  occurred  with  respect to the
Common  Stock  (such  exchange  ratio,  as  adjusted  from  time to time,  being
hereinafter referred to as the "Exchange Ratio").

                  Immediately  upon the action of the Board of  Directors of the
Company electing to exchange the Rights,  without any further action and without
any notice,  the right to  exercise  the Rights  will  terminate  and each Right
(other  than Rights that have  become  void  pursuant  to Section  4.1(b))  will
thereafter  represent  only the  right to  receive  a number of shares of Common
Stock equal to the  Exchange  Ratio.  Promptly  after the action of the Board of
Directors electing to exchange the Rights, the Company shall give notice thereof
(specifying  the steps to be taken to receive shares of Common Stock in exchange
for Rights) to the Rights Agent and the holders of the Rights (other than Rights
that have become void pursuant to Section 4.1(b)) Outstanding  immediately prior
thereto by mailing such notice in accordance with Section 5.9.

                  Each Person in whose name any certificate for shares is issued
upon the exchange of Rights  pursuant to this Section  4.1(c) or Section  4.1(d)
shall for all  purposes  be deemed to have  become  the  holder of record of the
shares  represented  thereby on,



                                       33


and such  certificate  shall be dated, the date upon which the Rights
Certificate  evidencing such Rights was duly  surrendered and payment of any
applicable  taxes and other  governmental  charges payable by the holder was
made; provided,  however,  that if the date of such surrender and payment is a
date upon which the stock transfer books of the Company are closed, such Person
shall be deemed to have become the record  holder of such shares on, and such
certificate  shall be dated, the next succeeding  Business Day on which the
stock transfer books of the Company are open.

                  (d) Whenever the Company shall become  obligated under Section
4.1(a) or (c) to issue  shares of Common  Stock upon  exercise of or in exchange
for Rights,  the  Company,  at its option,  may  substitute  therefor  shares of
Preferred  Stock, at a ratio of one  one-hundredth of a share of Preferred Stock
for each share of Common Stock so issuable.

                  (e) In the event that there shall not be sufficient authorized
but unissued  shares of Common Stock or Preferred Stock of the Company to permit
the exercise or exchange in full of the Rights in accordance with Section 4.1(a)
or (c),  the Company  shall  either (i) call a meeting of  stockholders  seeking
approval to cause sufficient  additional shares to be authorized  (provided that
if such  approval is not obtained the Company will take the action  specified in
clause (ii) of this  sentence) or (ii) take such action as shall be necessary to
ensure and provide, to the extent permitted by applicable law and any agreements
or instruments in effect on the Stock  Acquisition  Date to which it is a party,
that each Right shall  thereafter  constitute  the right to receive,


                                       34



(x) at the Company's  option,  either (A) in return for the Exercise Price,
debt or equity securities or other assets (or a combination  thereof) having a
fair value equal to twice the Exercise Price, or (B) without payment of
consideration  (except as otherwise required by applicable law), debt or equity
securities or other assets (or a combination  thereof)  having a fair value
equal to the Exercise Price, or (y) if the Board of  Directors  of the Company
elects to exchange the Rights in accordance with Section 3.1(c),  debt or equity
securities or other assets (or a combination  thereof)  having a fair  value
equal to the  product of the Market Price of a share of Common Stock on the
Flip-in Date times the Exchange Ratio in effect on the Flip-in Date,  where in
any case set forth in (x) or (y) above the fair  value  of such  debt or  equity
securities  or other  assets  shall be as determined  in good  faith  by the
Board of  Directors  of the  Company,  after consultation with a nationally
recognized investment banking firm.

                  4.2 Flip-over.  (a) Prior to the Expiration  Date, the Company
shall not enter into any  agreement  with  respect to,  consummate  or permit to
occur any Flip-over  Transaction or Event unless and until it shall have entered
into a supplemental  agreement with the Flip-over Entity, for the benefit of the
holders of the Rights,  providing that,  upon  consummation or occurrence of the
Flip-over  Transaction or Event (i) each Right shall  thereafter  constitute the
right to purchase from the Flip-over Entity, upon exercise thereof in accordance
with the terms hereof, that number of shares of Flip-over Stock of the Flip-over
Entity  having  an  aggregate  Market  Price  on the  date  of  consummation  or
occurrence of such  Flip-over  Transaction  or Event equal to twice the



                                       35



Exercise Price  for an amount  in cash  equal to the  Exercise  Price  (such
right to be appropriately  adjusted  in order to protect  the  interests  of the
holders of Rights generally in the event that after such date of consummation or
occurrence an event of a type analogous to any of the events described in
Section 3.4(a) or (b) shall  have  occurred  with  respect  to the  Flip-over
Stock) and (ii) the Flip-over Entity shall thereafter be liable for, and shall
assume, by virtue of such Flip-over Transaction or Event and such supplemental
agreement,  all the obligations and duties of the Company pursuant to this
Agreement. The provisions of this Section 4.2 shall apply to successive
Flip-over Transactions or Events.

                  (b) Prior to the  Expiration  Date,  unless the Rights will be
redeemed  pursuant to Section 5.1 hereof in  connection  therewith,  the Company
shall not enter into any  agreement  with  respect to,  consummate  or permit to
occur any  Flip-over  Transaction  or Event if at the time thereof there are any
rights, warrants or securities outstanding or any other arrangements, agreements
or  instruments  that would  eliminate  or  otherwise  diminish in any  material
respect the  benefits  intended to be afforded by this Rights  Agreement  to the
holders of Rights upon consummation of such transaction.

                                   ARTICLE V

                                 MISCELLANEOUS

                  5.1 Redemption. (a) The Board of Directors of the Company may,
at its option, by a vote which includes the concurrence, by affirmative vote, of
a majority



                                       36



of the  Disinterested  Directors,  at any time prior to the close of business on
the Flip-in Date, elect to redeem all (but not less than all) of the then
outstanding Rights at the Redemption Price and the Company,  at its option, may
pay the  Redemption  Price either in cash or shares of Common Stock or other
securities  of the  Company  deemed by the Board of  Directors,  by a vote which
includes  the   concurrence,   by  affirmative   vote,  of  a  majority  of  the
Disinterested Directors, in the exercise of its sole discretion,  to be at least
equivalent in value to the Redemption Price.

                  (b)  Immediately  upon the action of the Board of Directors of
the Company electing to redeem the Rights (or, if the resolution of the Board of
Directors  electing to redeem the Rights states that the redemption  will not be
effective  until the  occurrence of a specified  future time or event,  upon the
occurrence of such future time or event), without any further action and without
any notice,  the right to exercise the Rights will terminate and each Right will
thereafter  represent only the right to receive the Redemption  Price in cash or
securities,  as determined by the Board of Directors.  Promptly after the Rights
are  redeemed,  the Company  shall give notice of such  redemption to the Rights
Agent and the holders of the then  outstanding  Rights by mailing such notice in
accordance with Section 5.9.

                  5.2 Expiration.  The Rights and this Agreement shall expire at
the  Expiration  Date and no  Person  shall  have any  rights  pursuant  to this
Agreement  or any Right after the  Expiration  Date,  except,  if the Rights are
exchanged or redeemed, as provided in Section 3.1 or 5.1 hereof.



                                       37



                  5.3 Issuance of New Rights  Certificates.  Notwithstanding any
of the  provisions  of this  Agreement  or of the  Rights to the  contrary,  the
Company may, at its option,  issue new Rights Certificates  evidencing Rights in
such form as may be approved by its Board of Directors to reflect any adjustment
or change in the  number  or kind or class of shares of stock  purchasable  upon
exercise of Rights made in accordance with the provisions of this Agreement.  In
addition,  in connection  with the issuance or sale of shares of Common Stock by
the Company  following  the  Separation  Date and prior to the  Expiration  Date
pursuant to the terms of securities  convertible  or  redeemable  into shares of
Common  Stock or to  options,  in each case  issued  or  granted  prior to,  and
outstanding  at, the Separation  Date, the Company shall issue to the holders of
such shares of Common Stock,  Rights  Certificates  representing the appropriate
number of Rights  in  connection  with the  issuance  or sale of such  shares of
Common Stock;  provided,  however,  in each case, (i) no such Rights Certificate
shall be issued,  if, and to the extent  that,  the Company  shall be advised by
counsel that such issuance would create a significant  risk of material  adverse
tax  consequences  to  the  Company  or  to  the  Person  to  whom  such  Rights
Certificates would be issued,  (ii) no such Rights  Certificates shall be issued
if, and to the extent that,  appropriate  adjustment  shall have  otherwise been
made in lieu of the  issuance  thereof,  and (iii)  the  Company  shall  have no
obligation  to  distribute  Rights  Certificates  to  any  Acquiring  Person  or
Affiliate or Associate of an Acquiring  Person or any  transferee  of any of the
foregoing.



                                       38




                  5.4  Supplements  and  Amendments.  The Company and the Rights
Agent may from time to time  supplement  or amend  this  Agreement  without  the
approval  of any  holders  of Rights (i) prior to the close of  business  on the
Flip-in Date, in any respect and (ii) after the close of business on the Flip-in
Date,  to make any changes that the Company may deem  necessary or desirable and
which shall not  materially  adversely  affect the  interests  of the holders of
Rights  generally or in order to cure any  ambiguity or to correct or supplement
any  provision  contained  herein  which  may be  inconsistent  with  any  other
provisions herein or otherwise defective. The Rights Agent will duly execute and
deliver any  supplement  or  amendment  hereto  requested  by the Company  which
satisfies the terms of the preceding sentence.

                  5.5  Fractional  Shares.  If the  Company  elects not to issue
certificates  representing  fractional  shares upon  exercise or  redemption  of
Rights, the Company shall, in lieu thereof,  in the sole discretion of the Board
of Directors,  either (a) evidence such fractional shares by depositary receipts
issued pursuant to an appropriate agreement between the Company and a depositary
selected by it,  providing  that each holder of a depositary  receipt shall have
all of the rights,  privileges  and  preferences  to which such holder  would be
entitled as a beneficial owner of such fractional share, or (b) sell such shares
on behalf of the  holders  of Rights and pay to the  registered  holders of such
Rights the appropriate fraction of price per share received upon such sale.

                  5.6 Rights of Action.  Subject to the terms of this  Agreement
(including Section 4.1(b)), rights of action in respect of this Agreement, other
than  rights of action



                                       39





vested  solely in the  Rights  Agent,  are vested in the respective  holders of
the  Rights;  and any holder of any  Rights,  without the consent of the Rights
Agent or of the holder of any other  Rights,  may, on such holder's  own behalf
and for such  holder's own benefit and the benefit of other holders of Rights,
enforce,  and may institute and maintain any suit, action or proceeding against
the Company to enforce,  or otherwise act in respect of, such holder's right to
exercise such holder's  Rights in the manner  provided in such holder's  Rights
Certificate  and  in  this  Agreement.  Without  limiting  the foregoing or any
remedies available to the holders of Rights, it is specifically acknowledged
that the holders of Rights would not have an adequate remedy at law for any
breach of this Agreement and will be entitled to specific performance of the
obligations  under,  and  injunctive  relief  against  actual or threatened
violations of, the obligations of any Person subject to this Agreement.

                  5.7  Rights  Holder Not Deemed a  Stockholder.  No holder,  as
such,  of any Rights shall be entitled to vote,  receive  dividends or be deemed
for any  purpose the holder of shares or any other  securities  which may at any
time be issuable on the exercise of such Rights,  nor shall  anything  contained
herein or in any Rights  Certificate  be  construed to confer upon the holder of
any Rights,  as such,  any of the rights of a stockholder  of the Company or any
right to vote for the  election of  directors  or upon any matter  submitted  to
stockholders  at any  meeting  thereof,  or to give or  withhold  consent to any
corporate  action,  or to receive notice of meetings or other actions  affecting
stockholders (except as provided in Section 5.8 hereof), or to receive dividends




                                       40



or  subscription  rights,  or  otherwise,  until  such  Rights  shall  have been
exercised or exchanged in accordance with the provisions hereof.

                  5.8 Notice of  Proposed  Actions.  In case the  Company  shall
propose after the Separation Date and prior to the Expiration Date (i) to effect
or permit occurrence of any Flip-over Transaction or Event or (ii) to effect the
liquidation,  dissolution or winding up of the Company, then, in each such case,
the Company shall give to each holder of a Right, in accordance with Section 5.9
hereof, a notice of such proposed action,  which shall specify the date on which
such Flip-over Transaction or Event, liquidation,  dissolution, or winding up is
to take place, and such notice shall be so given at least 20 Business Days prior
to the date of the taking of such proposed action.

                  5.9 Notices. Notices or demands authorized or required by this
Agreement to be given or made by the Rights Agent or by the holder of any Rights
to or on the Company shall be sufficiently given or made if delivered or sent by
first-class mail, postage prepaid,  addressed (until another address is filed in
writing with the Rights Agent) as follows:

                           HCIA Inc.
                           300 East Lombard Street
                           Baltimore, Maryland 21202

                           Attention:  Secretary and General Counsel

Any notice or demand  authorized  or required by this  Agreement  to be given or
made by the  Company or by the  holder of any  Rights to or on the Rights  Agent
shall be



                                       41




sufficiently  given or made if delivered or sent by first-class  mail, postage
prepaid,  addressed (until another address is filed in writing with the Company)
as follows:

                           ChaseMellon Shareholder Services
                           8306 Mills Drive
                           Suite 560
                           Miami, Florida 33183

Notices or demands  authorized or required by this Agreement to be given or made
by the  Company or the Rights  Agent to or on the holder of any Rights  shall be
sufficiently  given or made if delivered or sent by  first-class  mail,  postage
prepaid,  addressed  to such  holder at the address of such holder as it appears
upon the registry books of the Rights Agent or, prior to the Separation Date, on
the registry books of the transfer agent for the Common Stock.  Any notice which
is mailed in the manner herein  provided  shall be deemed given,  whether or not
the holder receives the notice.

                  5.10  Suspension  of  Exercisability.  To the extent  that the
Company determines in good faith that some action will or need be taken pursuant
to Section 4.1 or to comply with federal or state  securities  laws, the Company
may suspend the exercisability of the Rights for a reasonable period in order to
take such action or comply with such laws. In the event of any such  suspension,
the Company shall issue as promptly as practicable a public announcement stating
that the  exercisability or  exchangeability  of the Rights has been temporarily
suspended. Notice thereof pursuant to Section 5.9 shall not be required.

                  Failure to give a notice  pursuant to the  provisions  of this
Agreement shall not affect the validity of any action taken hereunder.



                                       42



                  5.11 Costs of  Enforcement.  The  Company  agrees  that if the
Company  or any  other  Person  the  securities  of which are  purchasable  upon
exercise  of Rights  fails to fulfill  any of its  obligations  pursuant to this
Agreement,  then the  Company or such Person  will  reimburse  the holder of any
Rights for the costs and expenses (including legal fees) incurred by such holder
in  actions to  enforce  such  holder's  rights  pursuant  to any Rights or this
Agreement.

                  5.12  Successors.  All the  covenants  and  provisions of this
Agreement  by or for the benefit of the  Company or the Rights  Agent shall bind
and inure to the benefit of their respective successors and assigns hereunder.

                  5.13  Benefits of this  Agreement.  Nothing in this  Agreement
shall be  construed  to give to any Person  other than the  Company,  the Rights
Agent and the  holders  of the Rights any legal or  equitable  right,  remedy or
claim  under  this  Agreement  and  this  Agreement  shall  be for the  sole and
exclusive  benefit  of the  Company,  the  Rights  Agent and the  holders of the
Rights.

                  5.14 Determination and Actions by the Board of Directors, etc.
The  Board of  Directors  of the  Company  shall  have the  exclusive  power and
authority to  administer  this  Agreement  and to exercise all rights and powers
specifically  granted to the Board or to the Company,  or as may be necessary or
advisable  in  the   administration  of  this  Agreement,   including,   without
limitation,  the  right  and  power  to (i)  interpret  the  provisions  of this
Agreement and (ii) make all determinations deemed necessary or advisable for the
administration   of   this   Agreement.   All   such   actions,    calculations,




                                       43




interpretations and determinations (including, for purposes of clause (y) below,
all omissions with respect to the foregoing) which are done or made by the Board
in good faith,  shall (x) be final,  conclusive and binding on the Company,  the
Rights  Agent,  the  holders of the Rights  and all other  parties,  and (y) not
subject the Board of Directors of the Company to any liability to the holders of
the Rights.




                  5.15  Severability.  If any term or  provision  hereof  or the
application  thereof to any  circumstance  shall, in any jurisdiction and to any
extent, be invalid or unenforceable, such term or provision shall be ineffective
as to such  jurisdiction  to the extent of such  invalidity or  unenforceability
without  invalidating  or  rendering   unenforceable  the  remaining  terms  and
provisions  hereof or the application of such term or provision to circumstances
other than those as to which it is held invalid or unenforceable.

                  5.16 Governing  Law.  THIS  AGREEMENT  AND EACH RIGHT  ISSUED
HEREUNDER  SHALL BE DEEMED TO BE A CONTRACT  MADE UNDER THE LAWS OF THE STATE OF
MARYLAND AND FOR ALL PURPOSES  SHALL BE GOVERNED BY AND  CONSTRUED IN ACCORDANCE
WITH THE LAWS OF SUCH STATE  APPLICABLE  TO CONTRACTS  TO BE MADE AND  PERFORMED
ENTIRELY WITHIN SUCH STATE.

                  5.17  Counterparts.  This  Agreement  may be  executed  in any
number of counterparts and each of such  counterparts  shall for all purposes be
deemed to be an




                                       44



original,  and all such counterparts  shall together  constitute but one and the
same instrument.

                  5.18 Descriptive  Headings.  Descriptive headings  appear
herein for  convenience  only and shall not control or affect the meaning or
construction of any of the provisions hereof.

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



ATTEST:                             HCIA INC.


__________________________          By:_____________________________________
                                       George D. Pillari
                                       President and Chief Executive Officer


ATTEST:                             CHASEMELLON SHAREHOLDER
                                     SERVICES, L.L.C.


__________________________          By:_____________________________________
                                       Name:
                                       Title:



                                       45









                                                                       EXHIBIT A
                                                                       ---------


                          [Form of Rights Certificate]

Certificate No.                                             _____________ Rights


                  THE  RIGHTS  ARE  SUBJECT  TO  REDEMPTION  OR
                  MANDATORY  EXCHANGE,  AT  THE  OPTION  OF THE
                  COMPANY, ON THE TERMS SET FORTH IN THE RIGHTS
                  AGREEMENT.   RIGHTS  BENEFICIALLY  OWNED  BY
                  ACQUIRING PERSONS OR AFFILIATES OR ASSOCIATES
                  THEREOF  (AS  SUCH TERMS  ARE DEFINED  IN THE
                  RIGHTS  AGREEMENT) OR  TRANSFEREES OF  ANY OF
                  THE FOREGOING WILL BE VOID.

                               Rights Certificate


                                   HCIA INC.

                  This  certifies  that  _______________________,  or registered
assigns,  is the registered holder of the number of Rights set forth above, each
of  which  entitles  the  registered  holder  thereof,  subject  to  the  terms,
provisions and conditions of the Stockholder Rights Agreement, dated as of April
23, l997 (as amended from time to time,  the "Rights  Agreement"),  between HCIA
Inc., a Maryland  corporation  (the  "Company"),  and ChaseMellon  Shareholder
Services,  as Rights Agent (the  "Rights  Agent",  which term shall  include any
successor Rights Agent under the Rights Agreement), to purchase from the Company
at any time  after the  Separation  Date (as such term is  defined in the Rights
Agreement)  and  prior  to  the  close  of  business  on  April  22,  2007,  one
one-hundredth  of a fully paid share of Class A Preferred Stock, par value $0.01
per share (the  "Preferred  Stock"),  of the Company  (subject to  adjustment as






provided in the Rights  Agreement) at the Exercise Price referred to below, upon
presentation and surrender of this Rights  Certificate with the Form of Election
to Exercise duly executed at the principal  office of the Rights Agent in Miami,
Florida.  The  Exercise  Price  shall  initially  be $240 per Right and shall be
subject to adjustment in certain events as provided in the Rights Agreement.

                  In certain  circumstances  described in the Rights  Agreement,
the Rights  evidenced  hereby  may  entitle  the  registered  holder  thereof to
purchase  securities of an entity other than the Company or securities or assets
of the  Company  other  than  Preferred  Stock,  all as  provided  in the Rights
Agreement.

                  This  Rights  Certificate  is  subject  to all  of the  terms,
provisions and conditions of the Rights Agreement,  which terms,  provisions and
conditions  are hereby  incorporated  herein by reference and made a part hereof
and to which Rights Agreement reference is hereby made for a full description of
the rights, limitations of rights, obligations,  duties and immunities hereunder
of the Rights  Agent,  the Company  and the holders of the Rights  Certificates.
Copies  of the  Rights  Agreement  are on file at the  principal  office  of the
Company and are available without cost upon written request.

                  This  Rights   Certificate,   with  or  without  other  Rights
Certificates,  upon  surrender at the office of the Rights Agent  designated for
such  purpose,  may be  exchanged  for  another  Rights  Certificate  or  Rights
Certificates of like tenor evidencing an aggregate number of Rights equal to the
aggregate  number  of  Rights  evidenced  by




                                       2



the  Rights  Certificate  or Rights Certificates surrendered. If this Rights
Certificate shall be exercised in part, the  registered  holder  shall be
entitled to receive,  upon  surrender  hereof, another Rights Certificate or
Rights Certificates for the number of whole Rights not exercised.

                  Subject to the provisions of the Rights Agreement,  each Right
evidenced by this  Certificate  may be (a) redeemed by the Company under certain
circumstances,  at its option,  at a redemption  price of $0.01 per Right or (b)
exchanged by the Company under  certain  circumstances,  at its option,  for one
share of Common Stock or one  one-hundredth  of a share of  Preferred  Stock per
Right (or, in certain cases, other securities or assets of the Company), subject
in  each  case to  adjustment  in  certain  events  as  provided  in the  Rights
Agreement.

                  No  holder  of this  Rights  Certificate,  as  such,  shall be
entitled to vote or receive dividends or be deemed for any purpose the holder of
any  securities  which may at any time be issuable on the exercise  hereof,  nor
shall  anything  contained  in the Rights  Agreement  or herein be  construed to
confer upon the holder  hereof,  as such,  any of the rights of a stockholder of
the  Company  or any right to vote for the  election  of  directors  or upon any
matter submitted to stockholders at any meeting thereof,  or to give or withhold
consent to any  corporate  action,  or to receive  notice of  meetings  or other
actions affecting stockholders (except as provided in the Rights Agreement),  or
to receive  dividends or  subscription  rights,  or otherwise,  until the Rights
evidenced by



                                       3



this Rights  Certificate  shall have been exercised or exchanged as provided in
the Rights Agreement.

                  This Rights  Certificate  shall not be valid or obligatory for
any purpose until it shall have been countersigned by the Rights Agent.

                  WITNESS the facsimile signature of the proper officers of the
Company and its corporate seal.

Date:  _____________________


ATTEST:                                  HCIA INC.



____________________________             By_____________________________________
Charles A. Berardesco                      George D. Pillari
Secretary                                  President and Chief Executive Officer


Countersigned:

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



By:_________________________
   Authorized Signature




                                       4





                  [Form of Reverse Side of Rights Certificate]



                               FORM OF ASSIGNMENT
                               ------------------

         (To be executed by the registered holder if such
         holder desires to transfer this Rights Certificate.)


                  FOR VALUE RECEIVED _____________________________ hereby sells,

assigns and transfers unto _____________________________________________________
                           (Please print name and address of transferee)

this  Rights Certificate,  together with all  right, title and interest therein,

and does hereby irrevocably constitute and appoint  _________________  Attorney,

to  transfer the  within Rights  Certificate on the  books of  the  within-named

Company, with full power of substitution.

Dated:  _____________________, ____

Signature Guaranteed:                          _________________________________
                                               Signature

                                               (Signature must correspond to
                                               name as written upon the face of
                                               this Rights Certificate in every
                                               particular, without alteration or
                                               enlargement or any change
                                               whatsoever)


                  Signatures  must  be  guaranteed  by  an  eligible   guarantor
institution  (banks,  stockbrokers,  savings  and loan  associations  and credit
unions with membership in an approved signature  guarantee  Medallion  program),
pursuant to SEC Rule 17AD-15.




- --------------------------------------------------------------------------------
                           (To be completed if true)







The undersigned hereby represents,  for the benefit of all holders of Rights and
shares of Common Stock, that the Rights evidenced by this Rights Certificate are
not, and, to the  knowledge of the  undersigned,  have never been,  Beneficially
Owned by an Acquiring Person or an Affiliate or Associate thereof (as defined in
the Rights Agreement).


                                               _________________________________
                                               Signature



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


                                     NOTICE
                                     ------

                  In  the  event  the  certification  set  forth  above  is  not
completed in connection with a purported  assignment,  the Company will deem the
Beneficial Owner of the Rights  evidenced by the enclosed Rights  Certificate to
be an Acquiring  Person or an Affiliate or Associate  thereof (as defined in the
Rights  Agreement) or a transferee of any of the foregoing and accordingly  will
deem  the  Rights  evidenced  by such  Rights  Certificate  to be  void  and not
transferable or exercisable.




                                       2






                  [To be attached to each Rights Certificate]


                          FORM OF ELECTION TO EXERCISE
                          ----------------------------

                   (To be  executed  if  holder  desires  to
                       exercise the Rights Certificate.)

TO:  HCIA INC.

                  The  undersigned   hereby   irrevocably   elects  to  exercise
__________________  whole Rights  represented by the attached Rights Certificate
to purchase the shares of  Preferred  Stock  issuable  upon the exercise of such
Rights and requests that certificates for such shares be issued in the name of:

                  ------------------------------------------
                  Address:
                  ------------------------------------------
                  ------------------------------------------
                  Social Security or Other Taxpayer
                  Identification Number:
                  ------------------------------------------

If such number of Rights  shall not be all the Rights  evidenced  by this Rights
Certificate,  a new Rights  Certificate  for the balance of such Rights shall be
registered in the name of and delivered to:


                  ------------------------------------------
                  Address:
                  ------------------------------------------
                  ------------------------------------------
                  Social Security or Other Taxpayer
                  Identification Number:
                  ------------------------------------------

Dated:     __________________, ____








Signature Guaranteed:                 __________________________________________
                                      Signature
                                      (Signature  must  correspond  to name as
                                      written upon the  face  of  the  attached
                                      Rights  Certificate  in  every particular,
                                      without  alteration  or  enlargement  or
                                      any change whatsoever)

                  Signatures must be guaranteed by a member firm of a registered
national securities exchange, a member of the National Association of Securities
Dealers,  Inc.,  or a  commercial  bank or trust  company  having  an  office or
correspondent in the United States.



- --------------------------------------------------------------------------------
                           (To be completed if true)

                  The  undersigned  hereby  represents,  for the  benefit of all
holders of Rights and shares of Common Stock,  that the Rights  evidenced by the
attached Rights  Certificate are not, and, to the knowledge of the  undersigned,
have never been,  Beneficially  Owned by an Acquiring  Person or an Affiliate or
Associate thereof (as defined in the Rights Agreement).




                                               _________________________________
                                               Signature



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


                                     NOTICE
                                     ------

                  In  the  event  the  certification  set  forth  above  is  not
completed in  connection  with a purported  exercise,  the Company will deem the
Beneficial Owner of the Rights  evidenced by the attached Rights  Certificate to
be an Acquiring  Person or an Affiliate or Associate  thereof (as defined in the
Rights  Agreement) or a transferee of any of the foregoing and accordingly  will
deem  the  Rights  evidenced  by such  Rights  Certificate  to be  void  and not
transferable or exercisable.



                                       2






                                                                       EXHIBIT B
                                                                       ---------

                                   HCIA INC.
                             ARTICLES SUPPLEMENTARY

                  HCIA INC., a Maryland  corporation having its principal office
in Baltimore  City,  Maryland  (hereinafter  called the  "Corporation"),  hereby
certifies to the State Department of Assessments and Taxation of Maryland that:

                  FIRST:  The  Corporation's  Amended and  Restated  Articles of
Incorporation,  as amended by Articles of  Amendment  thereto  (the  "Charter"),
currently provides for Five Hundred Thousand  (500,000)  authorized but unissued
shares of preferred  stock which may be  classified  by the Board of  Directors.
Pursuant to the authority  contained in the Charter,  the Board of Directors has
now  duly  classified  __________________________  shares  of the  Corporation's
authorized but unissued  preferred  stock, as a new class of preferred stock, to
be entitled "Class A Preferred Stock."

                  SECOND:  A  description  of the new class of Class A Preferred
Stock, and of the preferences,  rights, voting powers, restrictions,  dividends,
qualifications and terms and conditions thereof, is as follows:

Section 1.        Class A Preferred Stock.
- ----------        ------------------------

                  The Class A  Preferred  Stock  shall have a par value of $0.01
per share,  but shall have a stated value of One Hundred  Dollars  ($100.00) per
share. The Board of





Directors may from time to time classify additional unissued shares of Preferred
Stock as Class A Preferred Stock.

Section 2.        Dividends and Distributions.
- ----------        ----------------------------

                  The holders of record of full or fractional  shares of Class A
Preferred Stock shall be entitled to receive,  when and as declared by the Board
of  Directors,  but only out of funds  legally  available for the purpose (A) on
each date  that  dividends  or other  distributions  (other  than  dividends  or
distributions  payable in Common Stock of the  Corporation) are payable on or in
respect of Common Stock  comprising  part of the  Reference  Package (as defined
below),  an amount per whole share of this Series equal to the aggregate  amount
of  dividends or other  distributions  (other than  dividends  or  distributions
payable in Common Stock of the  Corporation)  that would be payable on such date
to a holder of the  Reference  Package  and (B) on the last day of March,  June,
September and December in each year, in an amount per whole share of this Series
equal to the excess (if any) of $60 over the aggregate  dividends paid per whole
share of this Series during the three month period ending on such last day. Each
such dividend shall be paid to the holders of record of shares of this Series on
the date,  not exceeding  sixty days  preceding  such  dividend or  distribution
payment  date,  fixed for the  purpose by the Board of  Directors  in advance of
payment of each particular dividend or distribution.  Dividends on each full and
each fractional share of this Series shall be cumulative from the date such full
or  fractional  share is  originally  issued;  provided  that  any such  full or
fractional share originally  issued after a dividend record date and on or


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prior to the  dividend  payment  date to which such record date  relates  shall
not be entitled to receive the dividend  payable on such  dividend  payment date
or any amount in respect of the period from such  original  issuance  to such
dividend payment date.

                  The term  "Reference  Package" shall initially mean 100 shares
of Common Stock, par value $0.01 per share ("Common Stock"), of the Corporation.
In the event the Corporation  shall at any time after the close of business  on,
April 24, 1997 (A) declare or pay a dividend on any Common Stock payable in 
Common Stock, (B) subdivide any Common Stock or (C) combine any Common Stock 
into a smaller number of shares, then and in each such case the Reference 
Package after such event  shall be the Common  Stock  that a holder of the  
Reference  Package immediately prior to such event would hold thereafter as a 
result thereof.

                  Holders of shares of this Series  shall not be entitled to any
dividends,  whether  payable  in cash,  property  or  stock,  in  excess of full
cumulative dividends, as herein provided on this Series.

                  So long as any  shares  of this  Series  are  outstanding,  no
dividend  (other than a dividend in Common  Stock or in any other stock  ranking
junior to this Series as to dividends and upon liquidation) shall be declared or
paid or set aside for  payment or other  distribution  declared or made upon the
Common  Stock or upon any  other  stock  ranking  junior  to this  Series  as to
dividends or upon liquidation, nor shall any Common Stock nor any other stock of
the  Corporation  ranking  junior  to or on a  parity  with  this  Series  as to
dividends or upon liquidation be redeemed,  purchased or otherwise



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acquired for any consideration (or any moneys be paid to or made available for a
sinking fund for the redemption of any shares of any such stock) by the
Corporation  (except by conversion  into or exchange for stock of the
Corporation  ranking junior to this Series as to dividends and upon
liquidation),  unless,  in each case,  the full cumulative dividends (including
the dividend to be due upon payment of such dividend,  distribution,
redemption,  purchase  or  other  acquisition)  on all outstanding  shares of
this Series shall have been,  or shall  contemporaneously be, paid.

Section 3.        Redemption.
- ----------        -----------

                  The shares of Class A Preferred Stock shall not be redeemable.

Section 4.        Liquidation Rights.
- ----------        -------------------

                  In the event of any liquidation,  dissolution or winding up of
the affairs of the Corporation, whether voluntary or involuntary, the holders of
full and  fractional  shares  of this  Series  shall  be  entitled,  before  any
distribution  or payment is made on any date to the holders of the Common  Stock
or any  other  stock of the  Corporation  ranking  junior  to this  Series  upon
liquidation,  to be paid in full an amount per whole share of this Series  equal
to the greater of (A) $24,000 or (B) the aggregate  amount  distributed or to be
distributed prior to such date in connection with such liquidation,  dissolution
or winding up to a holder of the Reference  Package  (such greater  amount being
hereinafter referred to as the "Liquidation Preference"),  together with accrued
dividends  to such  distribution  or  payment  date,  whether  or not  earned or
declared.  If such payment shall have been made in full to all holders of shares
of this Series, the holders of shares of this



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Series as such shall have no right or claim to any of the remaining assets of
the Corporation.

                  In the  event  the  assets of the  Corporation  available  for
distribution  to the  holders  of shares of this  Series  upon any  liquidation,
dissolution or winding up of the Corporation,  whether voluntary or involuntary,
shall be  insufficient  to pay in full all  amounts  to which such  holders  are
entitled pursuant to the first paragraph of this Section 4, no such distribution
shall be made on account of any shares of any other class or series of Preferred
Stock ranking on a parity with the shares of this Series upon such  liquidation,
dissolution  or winding up unless  proportionate  distributive  amounts shall be
paid on account of the shares of this Series,  ratably in proportion to the full
distributable   amounts  for  which  holders  of  all  such  parity  shares  are
respectively entitled upon such liquidation, dissolution or winding up.

                  Upon  the  liquidation,  dissolution  or  winding  up  of  the
Corporation,  the  holders of shares of this Series  then  outstanding  shall be
entitled to be paid out of assets of the Corporation  available for distribution
to its stockholders  all amounts to which such holders are entitled  pursuant to
the first  paragraph of this  Section 4 before any payment  shall be made to the
holders of Common  Stock or any other stock of the  Corporation  ranking  junior
upon liquidation to this Series.

                  For the  purposes  of this  Section  4, the  consolidation  or
merger  of,  or  binding  share  exchange  by,  the  Corporation  with any other
corporation  shall not be



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deemed to  constitute a  liquidation,  dissolution  or winding up of the
Corporation.

Section 5.        Merger, Consolidation.
- ----------        ----------------------

                  Except as otherwise  provided herein, the holders of shares of
Class A Preferred  Stock shall not have any rights herein to convert such shares
into or exchange  such shares for shares of any other class or classes or of any
other series of any class or classes of capital stock of the Corporation.

                  In the event of any merger, consolidation, reclassification or
other  transaction  in which the  shares of Common  Stock are  exchanged  for or
changed into other stock or securities,  cash and/or any other property, then in
any such case the  shares  of this  Series  shall at the same time be  similarly
exchanged or changed in an amount per whole share equal to the aggregate  amount
of stock,  securities,  cash and/or any other property (payable in kind), as the
case may be, that a holder of the Reference Package would be entitled to receive
as a result of such transaction.

Section 6.        Voting.
- ----------        -------

                  In  addition  to any other  vote or  consent  of  stockholders
required by law or by the Charter, each whole share of this Series shall, on any
matter,  vote as a class with any other  capital  stock  comprising  part of the
Reference  Package  and voting on such matter and shall have the number of votes
thereon that a holder of the Reference Package would have.




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Section 7.        Fractional Shares.
- ----------        ------------------

                  Class A  Preferred  Shares  may be  issued in  fractions  of a
share,  which may be represented by certificates or scrip for fractional shares,
or by depository receipts,  and which shall entitle the holder, in proportion to
such holder's  fractional shares, to exercise voting rights,  receive dividends,
participate  in  distributions  and to have the  benefit of all other  rights of
holders of Class A Preferred Stock.

                  THIRD: The classification of authorized but unissued shares as
set  forth in  these  Articles  Supplementary  has  effected  no  change  in the
authorized  capital  of the  Corporation  consisting  of Five  Hundred  Thousand
(500,000)  shares of  Preferred  Stock,  with a par  value of  $0.01,  and Fifty
Million  (50,000,000)  shares of Common  Stock,  with a par value of $0.01 each,
amounting in the aggregate to Five Hundred Five Thousand Dollars ($505,000).

                  IN WITNESS WHEREOF,  HCIA Inc. has caused these presents to be
signed in its name and on its behalf by its President and its corporate  seal to
be hereunto affixed and attested by its Secretary this ________ day of ________,
____ and the undersigned officers acknowledge that these Articles  Supplementary
are  the  acts  of  the  Corporation,  that  to the  best  of  their  knowledge,
information  and belief all matters and facts set forth  herein  relating to the
authorization and approval of these Articles are




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true in all material respects, and that this statement is made under the
penalties of perjury.


ATTEST:                                  HCIA INC.

_____________________________            By_____________________________________
Charles A. Berardesco                      George D. Pillari
Secretary                                  President and Chief Executive Officer



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