Exhibit 4.1

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                              REPLIGEN CORPORATION

                                       and

                     AMERICAN STOCK TRANSFER & TRUST COMPANY
                                 as Rights Agent

                                   ----------

                                RIGHTS AGREEMENT

                            Dated as of March 3, 2003

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                                TABLE OF CONTENTS

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<S>          <C>                                                                                   <C>
Section 1.   Certain Definitions ..............................................................     1

Section 2.   Appointment of Rights Agent ......................................................     5

Section 3.   Issue of Right Certificates ......................................................     5

Section 4.   Form of Right Certificates .......................................................     7

Section 5.   Countersignature and Registration ................................................     7

Section 6.   Transfer, Split Up, Combination and Exchange of Right Certificates; Mutilated,
             Destroyed, Lost or Stolen Right Certificates .....................................     7

Section 7.   Exercise of Rights; Purchase Price; Expiration Date of Rights ....................     8

Section 8.   Cancellation and Destruction of Right Certificates ...............................     9

Section 9.   Status and Availability of Preferred Shares ......................................     9

Section 10.  Preferred Shares Record Date .....................................................    10

Section 11.  Adjustment of Purchase Price, Number of Shares or Number of Rights ...............    10

Section 12.  Certificate of Adjustment ........................................................    17

Section 13.  Consolidation, Merger or Sale or Transfer of Assets or Earning Power .............    17

Section 14.  Fractional Rights and Fractional Shares ..........................................    18

Section 15.  Rights of Action .................................................................    19

Section 16.  Agreement of Right Holders .......................................................    20

Section 17.  Right Certificate Holder Not Deemed a Stockholder ................................    20

Section 18.  Concerning the Rights Agent ......................................................    20

Section 19.  Merger or Consolidation or Change of Name of Rights Agent ........................    21

Section 20.  Duties of Rights Agent ...........................................................    21

Section 21.  Change of Rights Agent ...........................................................    23

Section 22.  Issuance of New Right Certificates ...............................................    24

Section 23.  Redemption .......................................................................    24

Section 24.  Exchange .........................................................................    25

Section 25.  Notice of Certain Events .........................................................    26

Section 26.  Notices ..........................................................................    27

Section 27.  Supplements and Amendments .......................................................    28

Section 28.  Successors .......................................................................    28

Section 29.  Benefits of this Agreement .......................................................    28
</TABLE>


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<TABLE>
<S>          <C>                                                                                   <C>
Section 30.  Severability .....................................................................    28

Section 31.  Governing Law ....................................................................    28

Section 32.  Counterparts .....................................................................    28

Section 33.  Descriptive Headings; Construction ...............................................    28

Section 34.  Administration ...................................................................    29
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EXHIBITS:

Exhibit A   Form of Certificate of Designation of Series A Junior Participating
            Preferred Stock

Exhibit B   Form of Right Certificate

Exhibit C   Summary of Rights to Purchase Preferred Shares


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                                RIGHTS AGREEMENT

      Agreement, dated as of March 3, 2003, between Repligen Corporation, a
Delaware corporation (the "Company"), and American Stock Transfer & Trust
Company as rights agent (the "Rights Agent").

      WHEREAS, effective March 3, 2003, the Board of Directors of the Company
has authorized and declared a dividend of one preferred share purchase right (a
"Right") for each share of Common Stock, par value $0.01 per share, of the
Company (a "Common Share") outstanding on the Close of Business on March 17,
2003 (the "Record Date") and has authorized the issuance of one Right with
respect to each additional Common Share that shall become outstanding between
the Record Date and the earliest of Close of Business on the Distribution Date,
the Redemption Date and the Close of Business on the Final Expiration Date, each
Right representing the right to purchase one one-thousandth of a Preferred Share
(as hereinafter defined), or such different amount and/or kind of securities as
shall be hereinafter provided.

      NOW, THEREFORE, in consideration of the premises and the mutual agreements
herein set forth, the parties hereby agree as follows:

      Section 1. Certain Definitions. For purposes of this Agreement, the
following terms have the meanings indicated:

      "Acquiring Person" shall mean any Person who or which, together with all
Affiliates and Associates of such Person, shall be the Beneficial Owner of 15%,
or in the case of a Grandfathered Stockholder, 20%, or more of the Common Shares
of the Company then outstanding but shall not include (i) the Company, (ii) any
Subsidiary of the Company, (iii) any employee benefit plan of the Company or any
Subsidiary of the Company, or (iv) any entity holding Common Shares for or
pursuant to the terms of any such employee benefit plan. Notwithstanding the
foregoing:

            (1) no Person shall become an "Acquiring Person" as the result of an
      acquisition of Common Shares by the Company which, by reducing the number
      of shares outstanding, increases the proportionate number of shares
      beneficially owned by such Person to 15% (or such other percentage as
      would otherwise result in such person becoming an Acquiring Person) or
      more of the Common Shares of the Company then outstanding; provided,
      however, that if a Person shall so become the Beneficial Owner of 15% (or
      such other percentage) or more of the Common Shares of the Company then
      outstanding by reason of an acquisition of Common Shares by the Company
      and shall, after such share purchases by the Company, become the
      Beneficial Owner of an additional 1% of the outstanding Common Shares of
      the Company, then such Person shall be deemed to be an "Acquiring Person";
      and

            (2) if the Board of Directors of the Company determines in good
      faith that a Person who would otherwise be an "Acquiring Person," as
      defined pursuant to the


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      foregoing provisions of this paragraph, has become such inadvertently and
      without any plan or intention to seek or affect control of the Company,
      and such Person enters into an irrevocable commitment with the Company to
      divest, and thereafter divests in accordance with the terms of such
      commitment as promptly as practicable a sufficient number of Common Shares
      so that such Person would no longer be an "Acquiring Person," as defined
      pursuant to the foregoing provisions of this paragraph, then such Person
      shall not be deemed to have become an "Acquiring Person" for any purposes
      of this Agreement.

      "Affiliate" and "Associate" shall have the respective meanings ascribed to
such terms in Rule 12b-2 of the Exchange Act and Exchange Act Regulations, as in
effect on the date of this Agreement.

      A Person shall be deemed the "Beneficial Owner" of and shall be deemed to
"beneficially own" any securities:

            (i) which such Person or any of such Person's Affiliates or
      Associates beneficially owns, directly or indirectly, for purposes of
      Section 13(d) of the Exchange Act and Rule 13d-3 of the Exchange Act
      Regulations (or any comparable or successor law or regulation);

            (ii) which such Person or any of such Person's Affiliates or
      Associates has (A) the right to acquire (whether such right is exercisable
      immediately or only after the passage of time) pursuant to any agreement,
      arrangement or understanding (other than customary agreements with and
      between underwriters and selling group members with respect to a bona fide
      public offering of securities), written or otherwise, 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 of, or to beneficially own,
      securities tendered pursuant to a tender or exchange offer made pursuant
      to, and in accordance with, the applicable rules and regulations
      promulgated under the Exchange Act by or on behalf of such Person or any
      of such Person's Affiliates or Associates until such tendered securities
      are accepted for purchase or exchange; or (B) the right to vote pursuant
      to any agreement, arrangement or understanding; provided, however, that a
      Person shall not be deemed the Beneficial Owner of, or to beneficially
      own, any security if the agreement, arrangement or understanding to vote
      such security (1) arises solely from a revocable proxy or consent given to
      such Person in response to a public proxy or consent solicitation made
      pursuant to, and in accordance with, the applicable rules and regulations
      promulgated under the Exchange Act and (2) is not also then reportable on
      Schedule 13D under the Exchange Act (or any comparable or successor
      report); or

            (iii) which are beneficially owned, directly or indirectly, by any
      other Person (or any Affiliate or Associate thereof) with which such
      Person or any of such Person's Affiliates or Associates has any agreement,
      arrangement or understanding (other than customary agreements with and
      between underwriters and selling group members with respect to a bona fide
      public offering of securities), written or otherwise, for the purpose


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      of acquiring, holding, voting (except to the extent contemplated by the
      proviso to section (B) of the immediately preceding paragraph (ii)) or
      disposing of any securities of the Company; provided, however, that in no
      case shall an officer or director of the Company be deemed (A) the
      Beneficial Owner of any securities beneficially owned by another officer
      or director of the Company solely by reason of actions undertaken by such
      persons in their capacity as officers or directors of the Company or (B)
      the Beneficial Owner of securities held of record by the trustee of any
      employee benefit plan of the Company or any Subsidiary of the Company for
      the benefit of any employee of the Company or any Subsidiary of the
      Company, other than the officer or director, by reason of any influence
      that such officer or director may have over the voting of the securities
      held in the plan.

      Notwithstanding anything in this definition of Beneficial Ownership to the
contrary, the phrase "then outstanding," when used with reference to a Person's
Beneficial Ownership of securities of the Company, shall mean the number of such
securities then issued and outstanding together with the number of such
securities not then actually issued and outstanding which such Person would be
deemed to own beneficially hereunder.

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

      "Close of Business" on any given date shall mean 5:00 P.M., Boston,
Massachusetts time, on such date; provided, however, that if such date is not a
Business Day it shall mean 5:00 P.M., Boston, Massachusetts time, on the next
succeeding Business Day.

      "Common Shares" when used with reference to the Company shall mean the
shares of common stock, par value $0.01 per share, of the Company. "Common
Shares" when used with reference to any Person other than the Company shall mean
the capital stock (or equity interest) with the greatest voting power of such
other Person or, if such other Person is a Subsidiary of another Person, the
Person or Persons which ultimately control such first-mentioned Person.

      "Common Stock Equivalents" shall have the meaning set forth in Section
11(a)(iii)(B)(3) hereof.

      "Company" shall have the meaning set forth in the recitals to this
Agreement.

      "Current Per Share Market Price" shall have the meaning set forth in
Section 11(d)(i) hereof.

      "Current Value" shall have the meaning set forth in Section
11(a)(iii)(A)(1) hereof.

      "Distribution Date" shall have the meaning set forth in Section 3(a)
hereof.

      "Equivalent Preferred Shares" shall have the meaning set forth in Section
11(b) hereof.


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      "Exchange Act" shall mean the Securities Exchange Act of 1934, as amended.

      "Exchange Act Regulations" shall mean the General Rules and Regulations
under the Exchange Act.

      "Exchange Ratio" shall have the meaning set forth in Section 24(a) hereof.

      "Final Expiration Date" shall mean March 2, 2013.

      "Grandfathered Stockholder" shall mean BVF, Inc. and its Affiliates and
Associates, other than any Person who or which is not such an Affiliate or
Associate on the date of this Agreement and who or which subsequently acquires
direct or indirect control of BVF, Inc. without the prior written approval of
the board of directors of the Company.

      "Person" shall mean any individual, firm, corporation, partnership,
limited partnership, limited liability partnership, business trust, limited
liability company, unincorporated association or other entity, and shall include
any successor (by merger or otherwise) of such entity.

      "Preferred Shares" shall mean shares of Series A Junior Participating
Preferred Stock, par value $0.01 per share, of the Company having such rights
and preferences upon adoption as are set forth in the form of Certificate of
Designation set forth as Exhibit A hereto.

      "Purchase Price" shall have the meaning set forth in Section 7(b) hereof.

      "Record Date" shall have the meaning set forth in the recitals to this
Agreement.

      "Redemption Price" shall have the meaning set forth in Section 23(a)
hereof.

      "Right" shall have the meaning set forth in the recitals to this
Agreement.

      "Redemption Date" shall have the meaning set forth in Section 23(b)
hereof.

      "Right Certificate" shall mean a certificate evidencing a Right in
substantially the form of Exhibit B hereto.

      "Rights Agent" shall have the meaning set forth in the recitals to this
Agreement.

      "Section 11(a)(ii) Trigger Date" shall have the meaning set forth in
Section 11(a)(iii) hereof.

      "Shares Acquisition Date" shall mean the earlier of the date of (i) the
public announcement by the Company or an Acquiring Person that an Acquiring
Person has become such or (ii) the public disclosure of facts by the Company or
an Acquiring Person indicating that an Acquiring Person has become such.


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      "Spread" shall have the meaning set forth in Section 11(a)(iii)(A) hereof.

      "Subsidiary" of any Person shall mean any Person of which a majority of
the voting power of the voting equity securities or equity interest is owned,
directly or indirectly, by such Person.

      "Substitution Period" shall have the meaning set forth in Section
11(a)(iii) hereof. "Summary of Rights" shall mean the Summary of Rights to
Purchase Preferred Shares in substantially the form of Exhibit C hereto.

      "Trading Day" shall have the meaning set forth in Section 11(d)(i) hereof.

      Section 2. Appointment of Rights Agent. The Company hereby appoints the
Rights Agent to act as agent for the Company and the holders of the Rights (who,
in accordance with Section 3 hereof, shall prior to the Distribution Date also
be the holders of the Common Shares) in accordance with the terms and conditions
hereof, and the Rights Agent hereby accepts such appointment. The Company may
from time to time appoint such co-Rights Agents as it may deem necessary or
desirable, upon ten (10) days' prior written notice to the Rights Agent. The
Rights Agent shall have no duty to supervise, and in no event be liable for, the
acts or omissions of any such co-Rights Agent.

      Section 3. Issue of Right Certificates.

            (a) Until the earlier of (i) the Close of Business on the tenth
calendar day after the Shares Acquisition Date or (ii) the tenth Business Day
(or such later date as may be determined by action of the Board of Directors
prior to such time as any Person becomes an Acquiring Person) after the date of
the commencement by any Person (other than the Company, any Subsidiary of the
Company, any employee benefit plan of the Company or of any Subsidiary of the
Company or any entity holding Common Shares for or pursuant to the terms of any
such plan) of, or of the first public announcement of the intention of any
Person (other than any of the Persons referred to in the preceding
parenthetical) to commence, a tender or exchange offer the consummation of which
would result in any Person becoming the Beneficial Owner of Common Shares
aggregating 15% or, in the case of a Grandfathered Stockholder, 20% or more of
the then outstanding Common Shares (such date being herein referred to as the
"Distribution Date"), (x) the Rights will be evidenced (subject to the
provisions of Section 3(b) hereof) by the certificates for Common Shares
registered in the names of the holders thereof (which certificates shall also be
deemed to be Right Certificates) and not by separate Right Certificates, and (y)
the right to receive Right Certificates will be transferable only in connection
with the transfer of Common Shares. As soon as practicable after the
Distribution Date, the Company will prepare and execute, the Rights Agent will
countersign, and the Company will send or cause to be sent (and the Rights Agent
will, if requested, send) by first-class, insured, postage-prepaid mail, to each
record holder of Common Shares as of the Close of Business on the Distribution
Date, at the address of such holder shown on the records of the Company, a Right
Certificate evidencing one Right for each Common Share so held. As of the
Distribution Date, the Rights will be evidenced solely by such Right
Certificates.


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            (b) On the Record Date, or as soon as practicable thereafter, the
Company will send a copy of the Summary of Rights by first-class,
postage-prepaid mail, to each record holder of Common Shares as of the Close of
Business on the Record Date, at the address of such holder shown on the records
of the Company. With respect to certificates for Common Shares outstanding as of
the Record Date, until the Close of Business on the Distribution Date, the
Rights will be evidenced by such certificates registered in the names of the
holders thereof together with a copy of the Summary of Rights attached thereto.
Until the Close of Business on the Distribution Date (or the earlier of the
Redemption Date or the Close of Business on the Final Expiration Date), the
surrender for transfer of any certificate for Common Shares outstanding on the
Record Date, with or without a copy of the Summary of Rights attached thereto,
shall also constitute the transfer of the Rights associated with the Common
Shares evidenced thereby.

            (c) Certificates for Common Shares which become outstanding
(including, without limitation, reacquired Common Shares referred to in the last
sentence of this paragraph (c)) after the Record Date but prior to the earliest
of the Close of Business on the Distribution Date, the Redemption Date or the
Close of Business on the Final Expiration Date shall have impressed on, printed
on, written on or otherwise affixed to them the following legend:

            This certificate also evidences and entitles the holder hereof to
            certain Rights as set forth in a Rights Agreement between Repligen
            Corporation and American Stock Transfer & Trust Company, dated as of
            March 3, 2003 (the "Rights Agreement"), the terms of which are
            hereby incorporated herein by reference and a copy of which is on
            file at the principal executive offices of Repligen Corporation.
            Under certain circumstances, as set forth in the Rights Agreement,
            such Rights will be evidenced by separate certificates and will no
            longer be evidenced by this certificate. Repligen Corporation will
            mail to the holder of this certificate a copy of the Rights
            Agreement without charge after receipt of a written request
            therefor. Under certain circumstances, as set forth in the Rights
            Agreement, Rights that are or were acquired or beneficially owned by
            Acquiring Persons (as defined in the Rights Agreement) may become
            null and void.

With respect to such certificates containing the foregoing legend, until the
Close of Business on the Distribution Date, the Rights associated with the
Common Shares represented by certificates shall be evidenced by such
certificates alone, and the surrender for transfer of any such certificate shall
also constitute the transfer of the Rights associated with the Common Shares
represented thereby. In the event that the Company purchases or acquires any
Common Shares after the Record Date but prior to the Close of Business on the
Distribution Date, any Rights associated with such Common Shares shall be deemed
canceled and retired so that the Company shall not be entitled to exercise any
Rights associated with the Common Shares which are no longer outstanding.


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      Section 4. Form of Right Certificates. The Right Certificates (and the
forms of election to purchase Preferred Shares and of assignment to be printed
on the reverse thereof) shall be substantially the same as Exhibit B hereto and
may have 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 applicable law or with any rule or regulation made pursuant
thereto or with any rule or regulation of any stock exchange or transaction
reporting system on which the Rights may from time to time be listed, or to
conform to usage. Subject to the other provisions of this Agreement, the Right
Certificates shall entitle the holders thereof to purchase such number of one
one-thousandths of a Preferred Share as shall be set forth therein at the
Purchase Price, but the number of one one-thousandths of a Preferred Share and
the Purchase Price shall be subject to adjustment as provided herein.

      Section 5. Countersignature and Registration.

            (a) The Right Certificates shall be executed on behalf of the
Company by its Chairman of the Board, its Chief Executive Officer, its
President, any of its Vice Presidents, or its Chief Financial Officer, either
manually or by facsimile signature, shall have affixed thereto the Company's
seal or a facsimile thereof, and shall be attested by the Secretary or any
Assistant Secretary of the Company, either manually or by facsimile signature.
The Right Certificates shall be countersigned by the Rights Agent and shall not
be valid for any purpose unless so countersigned, either manually or by
facsimile. In case any officer of the Company who shall have signed any of the
Right Certificates shall cease to be such officer of the Company before
countersignature by the Rights Agent and issuance and delivery by the Company,
such Right Certificates, nevertheless, may be countersigned by the Rights Agent
and issued and delivered by the Company with the same force and effect as though
the person who signed such Right Certificates had not ceased to be such officer
of the Company; and any Right Certificate may be signed on behalf of the Company
by any person who, at the actual date of the execution of such Right
Certificate, shall be a proper officer of the Company to sign such Right
Certificate, although at the date of the execution of this Rights Agreement any
such person was not such an officer.

            (b) Following the Distribution Date, the Rights Agent will keep or
cause to be kept, at its principal office, books for registration of the
transfer of the Right Certificates issued hereunder. Such books shall show the
names and addresses of the respective holders of the Right Certificates, the
number of Rights evidenced on its face by each of the Right Certificates and the
date of each of the Right Certificates.

      Section 6. Transfer, Split Up, Combination and Exchange of Right
Certificates; Mutilated, Destroyed, Lost or Stolen Right Certificates.

            (a) Subject to the provisions of Section 14 hereof, at any time
after the Close of Business on the Distribution Date, and prior to the earlier
of the Redemption Date or the Close of Business on the Final Expiration Date,
any Right Certificate or Right Certificates (other than Right Certificates
representing Rights that have become void pursuant to Section 11(a)(ii) hereof


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or that have been exchanged pursuant to Section 24 hereof) may be transferred,
split up, combined or exchanged for another Right Certificate or Right
Certificates, entitling the registered holder to purchase a like number of one
one-thousandths of a Preferred Share as the Right Certificate or Right
Certificates surrendered then entitled such holder to purchase. Any registered
holder desiring to transfer, split up, combine or exchange any Right Certificate
or Right Certificates shall make such request in writing delivered to the Rights
Agent, and shall surrender the Right Certificate or Right Certificates to be
transferred, split up, combined or exchanged at the principal office of the
Rights Agent. Thereupon the Rights Agent shall countersign and deliver to the
person entitled thereto a Right Certificate or Right Certificates, as the case
may be, as so requested. The Company may require payment of a sum sufficient for
any tax or governmental charge that may be imposed in connection with any
transfer, split up, combination or exchange of Right Certificates.

            (b) Upon receipt by the Company and the Rights Agent of evidence
reasonably satisfactory to them of the loss, theft, destruction or mutilation of
a Right Certificate, and, in case of loss, theft or destruction, of indemnity or
security reasonably satisfactory to them, and, at the Company's request,
reimbursement to the Company and the Rights Agent of all reasonable expenses
incidental thereto, and upon surrender to the Rights Agent and cancellation of
the Right Certificate if mutilated, the Company will make and deliver a new
Right Certificate of like tenor to the Rights Agent for delivery to the
registered holder in lieu of the Right Certificate so lost, stolen, destroyed or
mutilated.

      Section 7. Exercise of Rights; Purchase Price; Expiration Date of Rights.

            (a) The registered holder of any Right Certificate (other than a
holder whose Rights have become void pursuant to Section 11(a)(ii) hereof or
have been exchanged pursuant to Section 24 hereof) may exercise the Rights
evidenced thereby in whole or in part at any time after the Distribution Date
upon surrender of the Right Certificate, with the form of election to purchase
on the reverse side thereof duly executed, to the Rights Agent at its principal
office, together with payment of the Purchase Price for each one one-thousandth
of a Preferred Share as to which the Rights are exercised, prior to the Close of
Business on the Final Expiration Date.

            (b) The purchase price for each one one-thousandth of a Preferred
Share to be purchased upon the exercise of a Right shall initially be fifty
dollars ($50.00) (the "Purchase Price"), shall be subject to adjustment from
time to time as provided in Sections 11 and 13 hereof and shall be payable in
lawful money of the United States of America in accordance with paragraph (c)
below.

            (c) Upon receipt of a Right Certificate representing exercisable
Rights, with the form of election to purchase and certificate duly executed,
accompanied by payment of the Purchase Price for the number of one
one-thousandths of a Preferred Share to be purchased, and an amount equal to any
applicable transfer tax required, to be paid by the holder of such Right
Certificate in accordance with Section 9 hereof in cash, or by certified check,
cashier's check or money order payable to the order of the Company, the Rights
Agent shall thereupon promptly (i) (A) requisition from any transfer agent of
the Preferred Shares certificates for the number of one


                                       8
<PAGE>

one-thousandths of a Preferred Share to be purchased and the Company hereby
irrevocably authorizes its transfer agent to comply with all such requests, or
(B) requisition from any depository agent for the Preferred Shares depository
receipts representing such number of one one-thousandths of a Preferred Share as
are to be purchased (in which case certificates for the Preferred Shares
represented by such receipts shall be deposited by the transfer agent with the
depository agent) and the Company hereby directs the depository agent to comply
with such request, (ii) when appropriate, requisition from the Company the
amount of cash to be paid in lieu of issuance of fractional Preferred Shares in
accordance with Section 14 hereof, (iii) after receipt of such certificates or
depository receipts, cause the same to be delivered to or upon the order of the
registered holder of such Right Certificate, registered in such name or names as
may be designated by such holder and (iv) when appropriate, after receipt,
deliver such cash to or upon the order of the registered holder of such Right
Certificate.

            (d) In case the registered holder of any Right Certificate shall
exercise less than all the Rights evidenced thereby, a new Right Certificate
evidencing Rights equivalent to the Rights remaining unexercised shall be issued
by the Rights Agent to the registered holder of such Right Certificate or to
such registered holder's duly authorized assigns, subject to the provisions of
Section 14 hereof.

            (e) Notwithstanding anything in this Agreement to the contrary,
neither the Rights Agent nor the Company shall be obligated to undertake any
action with respect to a registered holder upon the occurrence of any purported
exercise as set forth in this Section 7 unless such registered holder shall have
(i) completed and signed the certificate contained in the form of election to
purchase set forth on the reverse side of the Right Certificate surrendered for
such exercise and (ii) provided such additional evidence of the identity of the
Beneficial Owner (or former Beneficial Owner) or Affiliates or Associates
thereof as the Company shall reasonably request.

      Section 8. Cancellation and Destruction of Right Certificates. All Right
Certificates surrendered for the purpose of exercise, transfer, split up,
combination or exchange shall, if surrendered to the Company or to any of its
agents, be delivered to the Rights Agent for cancellation or in canceled form,
or, if surrendered to the Rights Agent, shall be canceled by it, and no Right
Certificates shall be issued in lieu thereof except as expressly permitted by
any of the provisions of this Rights Agreement. The Company shall deliver to the
Rights Agent for cancellation and retirement, and the Rights Agent shall so
cancel and retire, any other Right Certificate purchased or acquired by the
Company otherwise than upon the exercise thereof. The Rights Agent shall deliver
all canceled Right Certificates to the Company, or shall, at the written request
of the Company, destroy such canceled Right Certificates, and in such case shall
deliver a certificate of destruction thereof to the Company.

      Section 9. Status and Availability of Preferred Shares.

            (a) The Company covenants and agrees that it will take all such
action as may be necessary to ensure that all Preferred Shares delivered upon
exercise of Rights shall, at the


                                       9
<PAGE>

time of delivery of the certificates for such Preferred Shares (subject to
payment of the Purchase Price), be duly and validly authorized and issued and
fully paid and non-assessable shares.

            (b) The Company further covenants and agrees that it will pay when
due and payable any and all federal and state transfer taxes and charges which
may be payable in respect of the issuance or delivery of the Right Certificates
or of any Preferred Shares upon the exercise of Rights. The Company shall not,
however, be required to pay any transfer tax which may be payable in respect of
any transfer or delivery of Right Certificates to a person other than, or the
issuance or delivery of certificates or depository receipts for the Preferred
Shares in a name other than that of, the registered holder of the Right
Certificate evidencing Rights surrendered for exercise or to issue or to deliver
any certificates or depository receipts for Preferred Shares upon the exercise
of any Rights until any such tax shall have been paid (any such tax being
payable by the holder of such Right Certificate at the time of surrender) or
until it has been established to the Company's reasonable satisfaction that no
such tax is due.

            (c) The Company covenants and agrees that it will use its best
efforts to cause to be reserved and kept available, out of its authorized and
unissued Preferred Shares or any Preferred Shares held in its treasury, the
number of Preferred Shares that will be sufficient to permit the exercise in
full of all outstanding Rights in accordance with Section 7 hereof. Upon the
occurrence of any events resulting in an increase in the aggregate number of
shares of Preferred Stock (or other equity securities of the Company) issuable
upon exercise of all outstanding Rights above the number then reserved, the
Company shall make appropriate increases in the number of shares so reserved.

      Section 10. Preferred Shares Record Date. Each person in whose name any
certificate for Preferred Shares is issued upon the exercise of Rights shall for
all purposes be deemed to have become the holder of record of the Preferred
Shares represented thereby on, and such certificate shall be dated, the date
upon which the Right Certificate evidencing such Rights was duly surrendered and
payment of the Purchase Price (and any applicable transfer taxes) was made.
Prior to the exercise of the Rights evidenced thereby, the holder of a Right
Certificate shall not be entitled to any rights of a holder of Preferred Shares
for which the Rights shall be exercisable, including, without limitation, the
right to vote, to receive dividends or other distributions or to exercise any
preemptive rights, and shall not be entitled to receive any notice of any
proceedings of the Company, except as provided herein.

      Section 11. Adjustment of Purchase Price, Number of Shares or Number of
Rights. The Purchase Price, the number of Preferred Shares covered by each Right
and the number of Rights outstanding are subject to adjustment from time to time
as provided in this Section 11.

            (a) (i) In the event the Company shall at any time after the date of
this Agreement (A) declare a dividend on the Preferred Shares payable in
Preferred Shares, (B) subdivide the outstanding Preferred Shares, (C) combine
the outstanding Preferred Shares into a smaller number of Preferred Shares or
(D) issue any shares of its capital stock in a reclassification of the Preferred
Shares (including any such reclassification in connection with a consolidation
or merger in which the Company is the continuing or surviving corporation),


                                       10
<PAGE>

except as otherwise provided in this Section 11(a), the Purchase Price in effect
at the time of the record date for such dividend or of the effective date of
such subdivision, combination or reclassification, and the number and kind of
shares of capital stock issuable on such date, shall be proportionately adjusted
so that the holder of any Right exercised after such time shall be entitled to
receive the aggregate number and kind of shares of capital stock which, if such
Right had been exercised immediately prior to such date, such holder would have
owned upon such exercise and been entitled to receive by virtue of such
dividend, subdivision, combination or reclassification; provided, however, that
in no event shall the consideration to be paid upon the exercise of one Right be
less than the aggregate par value of the shares of capital stock of the Company
issuable upon exercise of one Right. If an event occurs which would require an
adjustment under both this Section 11(a)(i) and Section 11(a)(ii), the
adjustment provided for in this Section 11(a)(i) shall be in addition to, and
shall be made prior, to any adjustment required pursuant to Section 11(a)(ii).

                  (ii) Subject to the following paragraph of this subparagraph
(ii) and to Section 24 of this Agreement, in the event any Person shall become
an Acquiring Person, each holder of a Right shall thereafter have a right to
receive, upon exercise thereof at a price equal to the then current Purchase
Price multiplied by the number of one one-thousandths of a Preferred Share for
which a Right is then exercisable, in accordance with the terms of this
Agreement and in lieu of Preferred Shares, such number of Common Shares of the
Company as shall equal the result obtained by (x) multiplying the then current
Purchase Price by the number of one one-thousandths of a Preferred Share for
which a Right is then exercisable and dividing that product by (y) 50% of the
then current per share market price of the Company's Common Shares (determined
pursuant to Section 11(d) hereof) on the date such Person became an Acquiring
Person. In the event that any Person shall become an Acquiring Person and the
Rights shall then be outstanding, the Company shall not take any action that
would eliminate or diminish the benefits intended to be afforded by the Rights.

      From and after the occurrence of such an event, any Rights that are or
were acquired or beneficially owned by such Acquiring Person (or any Associate
or Affiliate of such Acquiring Person) on or after the earlier of (x) the date
of such event and (y) the Distribution Date shall be void and any holder of such
Rights shall thereafter have no right to exercise such Rights under any
provision of this Agreement. No Right Certificate shall be issued pursuant to
Section 3 that represents Rights beneficially owned by an Acquiring Person whose
Rights would be void pursuant to the preceding sentence or any Associate or
Affiliate thereof; no Right Certificate shall be issued at any time upon the
transfer of any Rights to an Acquiring Person whose Rights would be void
pursuant to the preceding sentence or any Associate or Affiliate thereof or to
any nominee of such Acquiring Person, Associate or Affiliate; and any Right
Certificate delivered to the Rights Agent for transfer to an Acquiring Person
whose Rights would be void pursuant to the preceding sentence or any Associate
or Affiliate thereof shall be canceled.

                  (iii) In the event that the number of Common Shares which are
authorized by the Company's certificate of incorporation and not outstanding or
subscribed for, or reserved or otherwise committed for issuance for purposes
other than upon exercise of the Rights, are not sufficient to permit the holder
of each Right to purchase the number of Common


                                       11
<PAGE>

Shares to which he would be entitled upon the exercise in full of the Rights in
accordance with the foregoing subparagraph (ii) of paragraph (a) of this Section
11, or should the Board of Directors so elect, the Company shall: (A) determine
the excess of (1) the value of the Common Shares issuable upon the exercise of a
Right (calculated as provided in the last sentence of this subparagraph (iii))
pursuant to Section 11(a)(ii) hereof (the "Current Value") over (2) the Purchase
Price (such excess, the "Spread"), and (B) with respect to each Right, make
adequate provision to substitute for such Common Shares, upon payment of the
applicable Purchase Price, any one or more of the following having an aggregate
value determined by the Board of Directors to be equal to the Current Value: (1)
cash, (2) a reduction in the Purchase Price, (3) Common Shares or other equity
securities of the Company (including, without limitation, shares, or units of
shares, of preferred stock which the Board of Directors of the Company has
determined to have the same value as shares of Common Stock (such shares of
preferred stock, "common stock equivalents")), (4) debt securities of the
Company, (5) other assets or (6) any combination of the foregoing, having an
aggregate value equal to the Current Value, where such aggregate value has been
determined by the Board of Directors of the Company, based upon the advice of a
nationally recognized investment banking firm selected by the Board of Directors
of the Company; provided, however, if the Company shall not have made adequate
provision to deliver value pursuant to clause (B) above within thirty (30) days
following the first occurrence of an event triggering the rights to purchase
Common Shares described in Section 11(a)(ii) (the end of such 30-day period, the
"Section 11(a)(ii) Trigger Date"), then the Company shall be obligated to
deliver, upon the surrender for exercise of a Right and without requiring
payment of the Purchase Price, shares of Common Stock (to the extent available)
and then, if necessary, cash, which shares and cash have an aggregate value
equal to the Spread. If the Board of Directors of the Company shall determine in
good faith that it is likely that sufficient additional Common Shares could be
authorized for issuance upon exercise in full of the Rights, the thirty (30) day
period set forth above may be extended to the extent necessary, but not more
than ninety (90) days after the Section 11(a)(ii) Trigger Date, in order that
the Company may seek stockholder approval for the authorization of such
additional shares (such period, as it may be extended, the "Substitution
Period"). To the extent that the Company determines that some action need be
taken pursuant to the first and/or second sentences of this Section 11(a)(iii),
the Company (x) shall provide, subject to the last paragraph of Section
11(a)(ii) hereof, that such action shall apply uniformly to all outstanding
Rights, and (y) may suspend the exercisability of the Rights until the
expiration of the Substitution Period in order to seek any authorization of
additional shares and/or to decide the appropriate form of distribution to be
made pursuant to such first sentence and to determine the value thereof. In the
event of any such suspension, the Company shall make a public announcement, and
shall deliver to the Rights Agent a statement, stating that the exercisability
of the Rights has been temporarily suspended. At such time as the suspension is
no longer in effect, the Company shall make another public announcement, and
deliver to the Rights Agent a statement, so stating. For purposes of this
Section 11(a)(iii), the value of the Common Shares shall be the current per
share market price (as determined pursuant to Section 11(d)(i) hereof) of the
Common Shares on the Section 11(a)(ii) Trigger Date and the value of any common
stock equivalent shall be deemed to have the same value as the Common Shares on
such date.

            (b) In the event that the Company shall fix a record date for the
issuance of rights, options or warrants to all holders of Preferred Shares
entitling them (for a period expiring


                                       12
<PAGE>

within 45 calendar days after such record date) to subscribe for or purchase
Preferred Shares (or shares having the same rights, privileges and preferences
as the Preferred Shares ("equivalent preferred shares")) or securities
convertible into Preferred Shares or equivalent preferred shares at a price per
Preferred Share or equivalent preferred share (or having a conversion price per
share, if a security convertible into Preferred Shares or equivalent preferred
shares) less than the then current per share market price of the Preferred
Shares (as defined in Section 11(d)) on such record date, the Purchase Price to
be in effect after such record date shall be adjusted by multiplying the
Purchase Price in effect immediately prior to such record date by a fraction,
the numerator of which shall be the number of Preferred Shares outstanding on
such record date plus the number of Preferred Shares which the aggregate
offering price of the total number of Preferred Shares and/or equivalent
preferred shares so to be offered (and/or the aggregate initial conversion price
of the convertible securities so to be offered) would purchase at such current
market price and the denominator of which shall be the number of Preferred
Shares outstanding on such record date plus the number of additional Preferred
Shares and/or equivalent preferred shares to be offered for subscription or
purchase (or into which the convertible securities so to be offered are
initially convertible); provided, however, that in no event shall the
consideration to be paid upon the exercise of one Right be less than the
aggregate par value of the shares of capital stock of the Company issuable upon
exercise of one Right. In case such subscription price may be paid in a
consideration part or all of which shall be in a form other than cash, the value
of such consideration shall be as determined in good faith by the Board of
Directors of the Company, whose determination shall be described in a statement
filed with the Rights Agent. Preferred Shares owned by or held for the account
of the Company shall not be deemed outstanding for the purpose of any such
computation. Such adjustment shall be made successively whenever such a record
date is fixed; and in the event that such rights, options or warrants are not so
issued, the Purchase Price shall be adjusted to be the Purchase Price which
would then be in effect if such record date had not been fixed.

            (c) In case the Company shall fix a record date for the making of a
distribution to all holders of the Preferred Shares (including any such
distribution made in connection with a consolidation or merger in which the
Company is the continuing or surviving corporation) of evidences of indebtedness
or assets (other than a regular quarterly cash dividend or a dividend payable in
Preferred Shares) or subscription rights or warrants (excluding those referred
to in Section 11(b) hereof), the Purchase Price to be in effect after such
record date shall be determined by multiplying the Purchase Price in effect
immediately prior to such record date by a fraction, the numerator of which
shall be the then current per share market price of the Preferred Shares on such
record date, less the fair market value (as determined in good faith by the
Board of Directors of the Company, whose determination shall be described in a
statement filed with the Rights Agent) of the portion of the assets or evidences
of indebtedness so to be distributed or of such subscription rights or warrants
applicable to one Preferred Share and the denominator of which shall be such
current per share market price of the Preferred Shares; provided, however, that
in no event shall the consideration to be paid upon the exercise of one Right be
less than the aggregate par value of the shares of capital stock of the Company
to be issued upon exercise of one Right. Such adjustments shall be made
successively whenever such a record date is fixed; and in the event that such
distribution is not so made, the Purchase Price


                                       13
<PAGE>

shall again be adjusted to be the Purchase Price which would then be in effect
if such record date had not been fixed.

            (d) (i) For the purpose of any computation hereunder, the "current
per share market price" of any security (a "Security" for the purpose of this
Section 11(d)(i)) on any date shall be deemed to be the average of the daily
closing prices per share of such Security for the 30 consecutive Trading Days
(as such term is hereinafter defined) immediately prior to such date; provided,
however, that in the event that the current per share market price of the
Security is determined during a period following the announcement by the issuer
of such Security of (A) a dividend or distribution on such Security payable in
shares of such Security or securities convertible into such shares, or (B) any
subdivision, combination or reclassification of such Security and prior to the
expiration of 30 Trading Days after the ex-dividend date for such dividend or
distribution, or the record date for such subdivision, combination or
reclassification, then, and in each such case, the current per share market
price shall be appropriately adjusted to reflect the current market price per
share equivalent of such Security. The closing price for each day shall be the
last sale price, regular way, or, in case no such sale takes place on such day,
the average of the closing bid and asked prices, regular way, in either case as
reported in the principal consolidated transaction reporting system with respect
to securities listed or admitted to trading on the Nasdaq National Market System
("NASDAQ"), if the Security is not listed or admitted to trading on the NASDAQ,
as reported in the principal consolidated transaction reporting system with
respect to securities listed on the principal national securities exchange on
which the Security is listed or admitted to trading or, if the Security is not
listed or admitted to trading on any national securities exchange, the last
quoted price or, if not so quoted, the average of the high bid and low asked
prices in the over-the-counter market, as reported by NASDAQ or such other
system then in use, or, if on any such date the Security is not 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 Security selected by the
Board of Directors of the Company. The term "Trading Day" shall mean a day on
which the principal national securities exchange on which the Security is listed
or admitted to trading is open for the transaction of business or, if the
Security is not listed or admitted to trading on any national securities
exchange, a Business Day.

                  (ii) For the purpose of any computation hereunder, the
"current per share market price" of the Preferred Shares shall be determined in
accordance with the method set forth in Section 11(d)(i). If the Preferred
Shares are not publicly traded, the "current per share market price" of the
Preferred Shares shall be conclusively deemed to be the current per share market
price of the Common Shares as determined pursuant to Section 11(d)(i)
(appropriately adjusted to reflect any stock split, stock dividend or similar
transaction occurring after the date hereof), multiplied by 1,000. If neither
the Common Shares nor the Preferred Shares are publicly held or so listed or
traded, "current per share market price" shall mean the fair value per share as
determined in good faith by the Board of Directors of the Company, whose
determination shall be described in a statement filed with the Rights Agent.

            (e) No adjustment in the Purchase Price shall be required unless
such adjustment would require an increase or decrease of at least 1% in the
Purchase Price; provided,


                                       14
<PAGE>

however, that any adjustments which by reason of this Section 11(e) are not
required to be made shall be carried forward and taken into account in any
subsequent adjustment. All calculations under this Section 11 shall be made to
the nearest cent or to the nearest one ten-millionth of a Preferred Share or one
ten-thousandth of any other share or security as the case may be.
Notwithstanding the first sentence of this Section 11(e), any adjustment
required by this Section 11 shall be made no later than three years from the
date of the transaction which requires such adjustment.

            (f) If as a result of an adjustment made pursuant to Section 11(a)
hereof, the holder of any Right thereafter exercised shall become entitled to
receive any shares of capital stock of the Company other than Preferred Shares,
the number of such other shares so receivable upon exercise of any Right shall
thereafter be subject to adjustment from time to time in a manner and on terms
as nearly equivalent as practicable to the provisions with respect to the
Preferred Shares contained in Section 11(a) through (c), inclusive, and the
provisions of Sections 7, 9, 10 and 13 with respect to the Preferred Shares
shall apply on like terms to any such other shares.

            (g) All Rights originally issued by the Company subsequent to any
adjustment made to the Purchase Price hereunder shall evidence the right to
purchase, at the adjusted Purchase Price, the number of one one-thousandths of a
Preferred Share purchasable from time to time hereunder upon exercise of the
Rights, all subject to further adjustment as provided herein.

            (h) Unless the Company shall have exercised its election as provided
in Section 11(i), upon each adjustment of the Purchase Price as a result of the
calculations made in Sections 11(b) and (c), each Right outstanding immediately
prior to the making of such adjustment shall thereafter evidence the right to
purchase, at the adjusted Purchase Price, that number of one one-thousandths of
a Preferred Share (calculated to the nearest one ten-millionth of a Preferred
Share) obtained by (i) multiplying (x) the number of one one-thousandths of a
share covered by a Right immediately prior to this adjustment by (y) the
Purchase Price in effect immediately prior to such adjustment of the Purchase
Price and (ii) dividing the product so obtained by the Purchase Price in effect
immediately after such adjustment of the Purchase Price.

            (i) The Company may elect on or after the date of any adjustment of
the Purchase Price to adjust the number of Rights in substitution for any
adjustment in the number of one one-thousandths of a Preferred Share purchasable
upon the exercise of a Right. Each of the Rights outstanding after such
adjustment of the number of Rights shall be exercisable for the number of one
one-thousandths of a Preferred Share for which a Right was exercisable
immediately prior to such adjustment. Each Right held of record prior to such
adjustment of the number of Rights shall become that number of Rights
(calculated to the nearest one hundred-thousandth) obtained by dividing the
Purchase Price in effect immediately prior to adjustment of the Purchase Price
by the Purchase Price in effect immediately after adjustment of the Purchase
Price. The Company shall make a public announcement of its election to adjust
the number of Rights, indicating the record date for the adjustment, and, if
known at the time, the amount of the adjustment to be made. This record date may
be the date on which the Purchase Price is adjusted or any day thereafter, but,
if the Right Certificates have been distributed, shall be at least 10 days


                                       15
<PAGE>

later than the date of the public announcement. If Right Certificates have been
distributed, upon each adjustment of the number of Rights pursuant to this
Section 11(i), the Company shall, as promptly as practicable, cause to be
distributed to holders of record of Right Certificates on such record date Right
Certificates evidencing, subject to Section 14 hereof, the additional Rights to
which such holders shall be entitled as a result of such adjustment, or, at the
option of the Company, shall cause to be distributed to such holders of record
in substitution and replacement for the Right Certificates held by such holders
prior to the date of adjustment, and upon surrender thereof, if required by the
Company, new Right Certificates evidencing all the Rights to which such holders
shall be entitled after such adjustment. Right Certificates to be so distributed
shall be issued, executed and countersigned in the manner provided for herein
and shall be registered in the names of the holders of record of Right
Certificates on the record date specified in the public announcement.

            (j) Irrespective of any adjustment or change in the Purchase Price
or the number of one one-thousandths of a Preferred Share issuable upon the
exercise of the Rights, the Right Certificates theretofore and thereafter issued
may continue to express the Purchase Price and the number of one one-thousandths
of a Preferred Share which were expressed in the initial Right Certificates
issued hereunder.

            (k) Before taking any action that would cause an adjustment reducing
the Purchase Price below one one-thousandth of the then par value of the
Preferred Shares issuable upon exercise of the Rights, the Company shall take
any corporate action which may, in the opinion of its counsel, be necessary in
order that the Company may validly and legally issue fully paid and
non-assessable Preferred Shares at such adjusted Purchase Price.

            (l) In any case in which this Section 11 shall require that an
adjustment in the Purchase Price be made effective as of a record date for a
specified event, the Company may elect to defer until the occurrence of such
event the issuing to the holder of any Right exercised after such record date of
the Preferred Shares and other capital stock or securities of the Company, if
any, issuable upon such exercise over and above the Preferred Shares and other
capital stock or securities of the Company, if any, issuable upon such exercise
on the basis of the Purchase Price in effect prior to such adjustment; provided,
however, that the Company shall deliver to such holder a due bill or other
appropriate instrument evidencing such holder's right to receive such additional
shares upon the occurrence of the event requiring such adjustment.

            (m) Anything in this Section 11 to the contrary notwithstanding, the
Company shall be entitled to make such reductions in the Purchase Price, in
addition to those adjustments expressly required by this Section 11, as and to
the extent that it in its sole discretion shall determine to be advisable in
order that any (i) combination or subdivision of the Preferred Shares, (ii)
issuance wholly for cash of any Preferred Shares at less than the current market
price, (iii) issuance wholly for cash of Preferred Shares or securities which by
their terms are convertible into or exchangeable for Preferred Shares, (iv)
dividends on Preferred Shares payable in Preferred Shares or (v) issuance of any
rights, options or warrants referred to hereinabove in Section 11(b), hereafter
made by the Company to holders of its Preferred Shares shall not be taxable to
such stockholders.


                                       16
<PAGE>

            (n) In the event that at any time after the date of this Agreement
and prior to the Distribution Date, the Company shall (i) declare or pay any
dividend on the Common Shares payable in Common Shares or (ii) effect a
subdivision, combination or consolidation of the Common Shares (by
reclassification or otherwise other than by payment of dividends in Common
Shares) into a greater or lesser number of Common Shares, then in any such case
(i) the number of one one-thousandths of a Preferred Share purchasable after
such event upon proper exercise of each Right shall be determined by multiplying
the number of one one-thousandths of a Preferred Share so purchasable
immediately prior to such event by a fraction, the numerator of which is the
number of Common Shares outstanding immediately before such event and the
denominator of which is the number of Common Shares outstanding immediately
after such event, and (ii) each Common Share outstanding immediately after such
event shall have issued with respect to it that number of Rights which each
Common Share outstanding immediately prior to such event had issued with respect
to it. The adjustments provided for in this Section 11(n) shall be made
successively whenever such a dividend is declared or paid or such a subdivision,
combination or consolidation is effected.

      Section 12. Certificate of Adjustment. Whenever an adjustment is made as
provided in Sections 11 and 13 hereof, the Company shall promptly (a) prepare a
certificate setting forth such adjustment, and a brief statement of the facts
accounting for such adjustment, (b) file with the Rights Agent and with each
transfer agent for the Common Shares or the Preferred Shares a copy of such
certificate and (c) mail a brief summary thereof to each holder of a Right
Certificate in accordance with Section 25 hereof. Notwithstanding the foregoing
sentence, the failure by the Company to make such certification or give such
notice shall not affect the validity of or the force or effect of the
requirement for such adjustment. The Rights Agent shall be fully protected in
relying on any such certificate and on any adjustment therein contained.

      Section 13. Consolidation, Merger or Sale or Transfer of Assets or Earning
Power. In the event that, at any time after a Person becomes an Acquiring
Person, directly or indirectly, (i) the Company shall consolidate with, or merge
with and into, any other Person, (ii) any Person shall consolidate with the
Company, or merge with and into the Company and the Company shall be the
continuing or surviving corporation of such merger and, in connection with such
merger, all or part of the Common Shares shall be changed into or exchanged for
stock or other securities of any other Person (or the Company) or cash or any
other property, or (iii) the Company shall sell or otherwise transfer (or one or
more of its Subsidiaries shall sell or otherwise transfer), in one or more
transactions, assets or earning power aggregating 50% or more of the assets or
earning power of the Company and its Subsidiaries (taken as a whole) to any
other Person other than the Company or one or more of its wholly-owned
Subsidiaries, then, and in each such case, proper provision shall be made so
that (A) each holder of a Right (except as otherwise provided herein) shall
thereafter have the right to receive, upon the exercise thereof at a price equal
to the then current Purchase Price multiplied by the number of one
one-thousandths of a


                                       17
<PAGE>

Preferred Share for which a Right is then exercisable, in accordance with the
terms of this Agreement and in lieu of Preferred Shares, such number of Common
Shares of such other Person (including the Company as successor thereto or as
the surviving corporation) as shall equal the result obtained by (x) multiplying
the then current Purchase Price by the number of one one-thousandths of a
Preferred Share for which a Right is then exercisable and dividing that product
by (y) 50% of the then current per share market price of the Common Shares of
such other Person (determined pursuant to Section 11(d) hereof) on the date of
consummation of such consolidation, merger, sale or transfer; (B) the issuer of
such Common Shares shall thereafter be liable for, and shall assume, by virtue
of such consolidation, merger, sale or transfer, all the obligations and duties
of the Company pursuant to this Agreement; (C) the term "Company" shall
thereafter be deemed to refer to such issuer; and (D) such issuer shall take
such steps (including, but not limited to, the reservation of a sufficient
number of its Common Shares in accordance with Section 9 hereof) in connection
with such consummation as may be necessary to assure that the provisions hereof
shall thereafter be applicable, as nearly as reasonably may be, in relation to
the Common Shares thereafter deliverable upon the exercise of the Rights. The
Company covenants and agrees that it shall not consummate any such
consolidation, merger, sale or transfer unless prior thereto the Company and
such issuer shall have executed and delivered to the Rights Agent a supplemental
agreement so providing. The Company shall not enter into any transaction of the
kind referred to in this Section 13 if at the time of such transaction there are
any rights, warrants, instruments or securities outstanding or any agreements or
arrangements which, as a result of the consummation of such transaction, would
eliminate or substantially diminish the benefits intended to be afforded by the
Rights. The provisions of this Section 13 shall similarly apply to successive
mergers or consolidations or sales or other transfers. For purposes hereof, the
"earning power" of the Company and its Subsidiaries shall be determined in good
faith by the Company's Board of Directors on the basis of the operating earnings
of each business operated by the Company and its Subsidiaries during the three
fiscal years preceding the date of such determination (or, in the case of any
business not operated by the Company or any Subsidiary during three full fiscal
years preceding such date, during the period such business was operated by the
Company or any Subsidiary).

      Section 14. Fractional Rights and Fractional Shares.

            (a) The Company shall not be required to issue fractions of Rights
or to distribute Right Certificates which evidence fractional Rights. In lieu of
such fractional Rights, there shall be paid to the registered holders of the
Right Certificates with regard to which such fractional Rights would otherwise
be issuable, an amount in cash equal to the same fraction of the current market
value of a whole Right. For the purposes of this Section 14(a), the current
market value of a whole Right shall be the closing price of the Rights for the
Trading Day immediately prior to the date on which such fractional Rights would
have been otherwise issuable. The closing price for any day shall be the last
sale price, regular way, or, in case no such sale takes place on such day, the
average of the closing bid and asked prices, regular way, in either case as
reported in the principal consolidated transaction reporting system with respect
to securities listed or admitted to trading on the New York Stock Exchange or,
if the Rights are not listed or admitted to trading on the New York Stock
Exchange, as reported in the principal consolidated transaction reporting system
with respect to securities listed on the principal national securities exchange
on which the Rights are listed or admitted to trading or, if the Rights are not
listed or admitted to trading on any national securities exchange, the last
quoted price or, if not so quoted, the average of the high bid and low asked
prices in the over-the-counter market, as reported by NASDAQ or such other
system then in use or, if on any such date the Rights are


                                       18
<PAGE>

not 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 Rights
selected by the Board of Directors of the Company. If on any such date no such
market maker is making a market in the Rights, the fair value of the Rights on
such date as determined in good faith by the Board of Directors of the Company
shall be used.

            (b) The Company shall not be required to issue fractions of
Preferred Shares (other than fractions which are integral multiples of one
one-thousandth of a Preferred Share) upon exercise of the Rights or to
distribute certificates which evidence fractional Preferred Shares (other than
fractions which are integral multiples of one one-thousandth of a Preferred
Share). Fractions of Preferred Shares in integral multiples of one
one-thousandth of a Preferred Share may, at the election of the Company, be
evidenced by depository receipts, pursuant to an appropriate agreement between
the Company and a depository selected by it; provided, that such agreement shall
provide that the holders of such depository receipts shall have all the rights,
privileges and preferences to which they are entitled as beneficial owners of
the Preferred Shares represented by such depository receipts. In lieu of
fractional Preferred Shares that are not integral multiples of one
one-thousandth of a Preferred Share, the Company shall pay to each registered
holder of Right Certificates at the time such Rights are exercised as herein
provided an amount in cash equal to the same fraction of the current market
value of one Preferred Share as the fraction of one Preferred Share that such
holder would otherwise receive upon the exercise of the aggregate number of
rights exercised by such holder. For the purposes of this Section 14(b), the
current market value of a Preferred Share shall be the closing price of a
Preferred Share (as determined pursuant to the second sentence of Section
11(d)(i) hereof) for the Trading Day immediately prior to the date of such
exercise.

            (c) The holder of a Right by the acceptance of the Right expressly
waives any right to receive fractional Rights or fractional shares upon exercise
of a Right (except as provided above).

      Section 15. Rights of Action. All rights of action in respect of this
Agreement, excepting the rights of action given to the Rights Agent under
Section 18 hereof, are vested in the respective registered holders of the Right
Certificates (and, prior to the Distribution Date, the registered holders of the
Common Shares); and any registered holder of any Right Certificate (or, prior to
the Distribution Date, of the Common Shares) may, without the consent of the
Rights Agent or of the holder of any other Right Certificate (or, prior to the
Distribution Date, of the Common Shares), on his own behalf and for his own
benefit, enforce, and may institute and maintain any suit, action or proceeding
against the Company to enforce, or otherwise act in respect of, his right to
exercise the Rights evidenced by such Right Certificate in the manner provided
in such Right 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.


                                       19
<PAGE>

      Section 16. Agreement of Right Holders. Every holder of a Right, by
accepting the same, consents and agrees with the Company and the Rights Agent
and with every other holder of a Right that:

            (a) prior to the Distribution Date, the Rights will be transferable
only in connection with the transfer of the Common Shares;

            (b) after the Distribution Date, the Right Certificates are
transferable only on the registry books maintained by the Rights Agent if
surrendered at the principal office of the Rights Agent, duly endorsed or
accompanied by a proper instrument of transfer with a completed form of
certification; and

            (c) the Company and the Rights Agent may deem and treat the person
in whose name the Right Certificate (or, prior to the Distribution Date, the
associated Common Shares certificate) is registered as the absolute owner
thereof and of the Rights evidenced thereby (notwithstanding any notations of
ownership or writing on the Right Certificates or the associated Common Shares
certificate made by anyone other than the Company or the Rights Agent) for all
purposes whatsoever, and neither the Company nor the Rights Agent shall be
affected by any notice to the contrary.

      Section 17. Right Certificate Holder Not Deemed a Stockholder. No holder,
as such, of any Right Certificate shall be entitled to vote, receive dividends
or be deemed for any purpose the holder of the Preferred Shares or any other
securities of the Company which may at any time be issuable on the exercise of
the Rights represented thereby nor shall anything contained herein or in any
Right Certificate be construed to confer upon the holder of any Right
Certificate, 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 25 hereof), or to receive dividends
or subscription rights, or otherwise, until the Right or Rights evidenced by
such Right Certificate shall have been exercised in accordance with the
provisions hereof.

      Section 18. Concerning the Rights Agent.

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


                                       20
<PAGE>

            (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 Right Certificate
or certificate for Preferred Shares or 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.

      Section 19. 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 shall be a party, or any corporation succeeding to
the corporate trust 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 21 hereof. In case
at the time such successor Rights Agent shall succeed to the agency created by
this Agreement, any of the Right Certificates shall have been countersigned but
not delivered, any such successor Rights Agent may adopt the countersignature of
the predecessor Rights Agent and deliver such Right Certificates so
countersigned; and in case at that time any of the Right Certificates shall not
have been countersigned, any successor Rights Agent may countersign such Right
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 Right Certificates
shall have the full force provided in the Right Certificates and in this
Agreement.

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

      Section 20. Duties of Rights Agent. The Rights Agent undertakes the duties
and obligations expressly set forth in this Agreement and no implied duties or
obligations shall be read into this Agreement against the Rights Agent. The
Rights Agent shall perform those duties and obligations upon the following terms
and conditions, by all of which the Company and the holders of Right
Certificates, by their acceptance thereof, shall be bound:

      (a) The Rights Agent may consult with legal counsel (who may be legal
counsel for the Company), and the opinion of such counsel shall 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.


                                       21
<PAGE>

            (b) Whenever in the performance of its duties under this Agreement
the Rights Agent shall deem 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 any one of the Chairman of the Board, the
President, a Vice President, the Treasurer or the Secretary of the Company and
delivered to the Rights Agent; and such certificate shall 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 shall be liable hereunder only for its own
negligence, bad faith or willful misconduct.

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

            (e) The Rights Agent shall not be under any responsibility in
respect of the validity of this Agreement or the execution and delivery hereof
(except the due execution hereof by the Rights Agent) or in respect of the
validity or execution of any Right Certificate (except its countersignature
thereof); nor shall it be responsible for any breach by the Company of any
covenant or condition contained in this Agreement or in any Right Certificate;
nor shall it be responsible for any adjustment required under the provisions of
Sections 11 or 13 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 evidenced by
Right Certificates after actual notice of any such adjustment); nor shall it by
any act hereunder be deemed to make any representation or warranty as to the
authorization or reservation of any shares of Preferred Shares to be issued
pursuant to this Agreement or any Right Certificate or as to whether any
Preferred Shares will, when so issued, be validly authorized and issued, 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 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
one of the Chairman of the Board, the President, a Vice President, the Secretary
or the Treasurer of the Company, and to apply to such officers for advice or
instructions in connection with its duties, and it shall not be liable for any
action taken or suffered to be taken by it in good faith in accordance with
instructions of any such officer.


                                       22
<PAGE>

            (h) The Rights Agent and any stockholder, director, officer or
employee of the Rights Agent may buy, sell or deal in any of the Rights or other
securities of the Company or become pecuniary 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 shall not be answerable or
accountable for any act, default, neglect or misconduct of any such attorneys or
agents or for any loss to the Company resulting from any such act, default,
neglect or misconduct, provided reasonable care was exercised in the selection
and continued employment thereof.

      Section 21. Change of Rights Agent. The Rights Agent or any successor
Rights Agent may resign and be discharged from its duties under this Agreement
upon 30 days' notice in writing mailed to the Company and to each transfer agent
of the Common Shares and the Preferred Shares by registered or certified mail,
and to the holders of the Right Certificates by first-class mail. The Company
may remove the Rights Agent or any successor Rights Agent upon 30 days' notice
in writing, mailed to the Rights Agent or successor Rights Agent, as the case
may be, and to each transfer agent of the Common Shares and the Preferred Shares
by registered or certified mail, and to the holders of the Right Certificates by
first-class mail. If the Rights Agent shall resign or be removed or shall
otherwise become incapable of acting, the Company shall appoint a successor to
the Rights Agent. If the Company shall fail to make such appointment within a
period of 30 days after giving notice of 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 a Right Certificate (who shall,
with such notice, submit his Right Certificate for inspection by the Company),
then the registered holder of any Right Certificate 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 any state of the United States, in good standing, which is authorized under
such laws to exercise corporate trust powers 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 $100
million. After appointment, the successor Rights Agent shall 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 shall file notice thereof in writing
with the predecessor Rights Agent and each transfer agent of the Common Shares
and the Preferred Shares, and mail a notice thereof in writing to the registered
holders of the Right Certificates. Failure to give any notice provided for in
this Section 21, 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.


                                       23
<PAGE>

      Section 22. Issuance of New Right Certificates. Notwithstanding any of the
provisions of this Agreement or of the Rights to the contrary, the Company may,
at its option, issue new Right Certificates evidencing Rights in such form as
may be approved by its Board of Directors to reflect any adjustment or change in
the Purchase Price and the number or kind or class of shares or other securities
or property purchasable under the Right Certificates made in accordance with the
provisions of this Agreement. In addition, in connection with the issuance or
sale of shares of Common Stock following the Distribution Date and prior to the
Final Expiration Date, the Company (a) shall, with respect to shares of Common
Stock so issued or sold pursuant to the exercise of stock options or under any
employee benefit plan or arrangement or upon the exercise, conversion or
exchange of securities of the Company currently outstanding or issued at any
time in the future by the Company and (b) may, in any other case, if deemed
necessary or appropriate by the Board of Directors of the Company, issue Right
Certificates representing the appropriate number of Rights in connection with
such issuance or sale; provided, however, that (i) no such Right Certificates
shall be issued and this sentence shall be null and void ab initio if, and to
the extent that, such issuance or this sentence would create a significant risk
of or result in material adverse tax consequences to the Company or the Person
to whom such Right Certificates would be issued or would create a significant
risk of or result in such options' or employee plans' or arrangements' failing
to qualify for otherwise available special tax treatment and (ii) no such Right
Certificates shall be issued if, and to the extent that, appropriate adjustment
shall otherwise have been made in lieu of the issuance thereof.

      Section 23. Redemption.

            (a) The Board of Directors of the Company may, at its option, at any
time prior to the earlier of (i) the Close of Business on the tenth calendar
date following the Shares Acquisition Date (or such later calendar date
following the Shares Acquisition Date as may be determined by the Board of
Directors in its sole discretion), or (ii) the Final Expiration Date, redeem all
but not less than all of the then outstanding Rights at a redemption price of
$0.001 per Right, appropriately adjusted to reflect any stock split, stock
dividend or similar transaction occurring after the date hereof (such redemption
price being hereinafter referred to as the "Redemption Price"). The redemption
of the Rights by the Board of Directors may be made effective at such time, on
such basis and subject to such conditions as the Board of Directors in its sole
discretion may establish.

            (b) Immediately upon the time of the effectiveness of the redemption
of the Rights pursuant to paragraph (a) of this Section 23 or such earlier time
as may be determined by the Board of Directors of the Company in the action
ordering such redemption (although not earlier than the time of such action)
(such time the "Redemption Date"), and without any further action and without
any notice, the right to exercise the Rights shall terminate and the only right
thereafter of the holders of Rights shall be to receive the Redemption Price.
The Company shall promptly give public notice of any such redemption; provided,
however, that the failure to give, or any defect in, any such notice shall not
affect the validity of such redemption. Within 10 days after such action of the
Board of Directors ordering the redemption of the Rights pursuant to paragraph
(a), the Company shall mail a notice of redemption to all the holders of the
then outstanding Rights at their last addresses as they appear upon the registry
books of the Rights


                                       24
<PAGE>

Agent or, prior to the Distribution Date, on the registry books of the transfer
agent for the Common Shares. Any notice which is mailed in the manner herein
provided shall be deemed given, whether or not the holder receives the notice.
If the payment of the Redemption Price is not included with such notice, each
such notice shall state the method by which the payment of the Redemption Price
will be made. Neither the Company nor any of its Affiliates or Associates may
redeem, acquire or purchase for value any Rights at any time in any manner other
than that specifically set forth in this Section 23 or in Section 24 hereof,
other than in connection with the purchase of Common Shares prior to the
Distribution Date.

      Section 24. Exchange.

            (a) The Board of Directors of the Company may, at its option, at any
time after any Person becomes an Acquiring Person, exchange all or part of the
then outstanding and exercisable Rights (which shall not include Rights that
have become void pursuant to the provisions of Section 11(a)(ii) hereof) for
Common Shares at an exchange ratio of one Common Share per Right, appropriately
adjusted to reflect any stock split, stock dividend or similar transaction
occurring after the date hereof (such exchange ratio being hereinafter referred
to as the "Exchange Ratio"). Notwithstanding the foregoing, the Board of
Directors shall not be empowered to effect such exchange at any time after any
Person (other than the Company, any Subsidiary of the Company, any employee
benefit plan of the Company or any such Subsidiary, or any entity holding Common
Shares for or pursuant to the terms of any such plan), together with all
Affiliates and Associates of such Person, becomes the Beneficial Owner of a
majority of the Common Shares then outstanding.

            (b) Immediately upon the action of the Board of Directors of the
Company ordering the exchange of any Rights pursuant to subsection (a) of this
Section 24 and without any further action and without any notice, the right to
exercise such Rights shall terminate and the only right thereafter of a holder
of such Rights shall be to receive that number of Common Shares equal to the
number of such Rights held by such holder multiplied by the Exchange Ratio. The
Company shall promptly give public notice of any such exchange; provided,
however, that the failure to give, or any defect in, such notice shall not
affect the validity of such exchange. The Company promptly shall mail a notice
of any such exchange to all of the holders of such Rights at their last
addresses as they appear upon the registry books of the Rights Agent. Any notice
which is mailed in the manner herein provided shall be deemed given, whether or
not the holder receives the notice. Each such notice of exchange will state the
method by which the exchange of the Common Shares for Rights will be effected
and, in the event of any partial exchange, the number of Rights which will be
exchanged. Any partial exchange shall be effected pro rata based on the number
of Rights (other than Rights which have become void pursuant to the provisions
of Section 11(a)(ii) hereof) held by each holder of Rights.

            (c) In any exchange pursuant to this Section 24, the Company, at its
option, may substitute Preferred Shares or common stock equivalents for Common
Shares exchangeable for Rights, at the initial rate of one one-thousandth of a
Preferred Share (or an appropriate number of common stock equivalents) for each
Common Share, as appropriately adjusted to reflect adjustments in the voting
rights of the Preferred Shares pursuant to the terms thereof, so


                                       25
<PAGE>

that the fraction of a Preferred Share delivered in lieu of each Common Share
shall have the same voting rights as one Common Share.

            (d) In the event that there shall not be sufficient Common Shares,
Preferred Shares or common stock equivalents authorized by the Company's
certificate of incorporation and not outstanding or subscribed for, or reserved
or otherwise committed for issuance for purposes other than upon exercise of
Rights, to permit any exchange of Rights as contemplated in accordance with this
Section 24, the Company shall take all such action as may be necessary to
authorize additional Common Shares, Preferred Shares or common stock equivalents
for issuance upon exchange of the Rights.

            (e) The Company shall not be required to issue fractions of Common
Shares or to distribute certificates which evidence fractional Common Shares. In
lieu of such fractional Common Shares, the Company shall pay to the registered
holders of the Right Certificates with regard to which such fractional Common
Shares would otherwise be issuable an amount in cash equal to the same fraction
of the current per share market value of a whole Common Share. For the purposes
of this paragraph (e), the current per share market value of a whole Common
Share shall be the closing price of a Common Share (as determined pursuant to
the second sentence of Section 11(d)(i) hereof) for the Trading Day immediately
prior to the date of exchange pursuant to this Section 24.

      Section 25. Notice of Certain Events.

            (a) In case the Company shall after the Distribution Date propose
(i) to pay any dividend payable in stock of any class to the holders of its
Preferred Shares or to make any other distribution to the holders of its
Preferred Shares (other than a regular quarterly cash dividend), (ii) to offer
to the holders of its Preferred Shares rights or warrants to subscribe for or to
purchase any additional Preferred Shares or shares of stock of any class or any
other securities, rights or options, (iii) to effect any reclassification of its
Preferred Shares (other than a reclassification involving only the subdivision
of outstanding Preferred Shares), (iv) to effect any consolidation or merger
into or with, or to effect any sale or other transfer (or to permit one or more
of its Subsidiaries to effect any sale or other transfer), in one or more
transactions, of 50% or more of the assets or earning power of the Company and
its Subsidiaries (taken as a whole) to, any other Person, (v) to effect the
liquidation, dissolution or winding up of the Company, or (vi) to declare or pay
any dividend on the Common Shares payable in Common Shares or to effect a
subdivision, combination or consolidation of the Common Shares (by
reclassification or otherwise than by payment of dividends in Common Shares),
then, in each such case, the Company shall give to each holder of a Right
Certificate, in accordance with Section 26 hereof, a notice of such proposed
action, which shall specify the record date for the purposes of such stock
dividend, or distribution of rights or warrants, or the date on which such
reclassification, consolidation, merger, sale, transfer, liquidation,
dissolution, or winding up is to take place and the date of participation
therein by the holders of the Common Shares and/or Preferred Shares, if any such
date is to be fixed, and such notice shall be so given in the case of any action
covered by clause (i) or (ii) above at least 10 days prior to the record date
for determining holders of the Preferred Shares for purposes of such action, and
in the case of any such other action, at least 10


                                       26
<PAGE>

days prior to the date of the taking of such proposed action or the date of
participation therein by the holders of the Common Shares and/or Preferred
Shares, whichever shall be the earlier.

            (b) In case any event set forth in Section 11(a)(ii) hereof shall
occur, then the Company shall as soon as practicable thereafter give to each
holder of a Right Certificate, in accordance with Section 26 hereof, a notice of
the occurrence of such event, which notice shall describe such event and the
consequences of such event to holders of Rights under Section 11(a)(ii) hereof.

      Section 26. Notices. Notices or demands authorized by this Agreement to be
given or made by the Rights Agent or by the holder of any Right Certificate to
or on the Company shall be sufficiently given or made if sent by first-class
mail, postage prepaid, addressed (until another address is filed in writing with
the Rights Agent) as follows:

                   Repligen Corporation
                   41 Seyon Street
                   Building 1, Suite100
                   Waltham, Massachusetts 02453

                   Attention: President

                   Copy to:

                   Testa, Hurwitz & Thibeault, LLP
                   125 High Street
                   Boston, Massachusetts 02110

                   Attention: Lawrence S. Wittenberg, Esq.

      Subject to the provisions of Section 21 hereof, any notice or demand
authorized by this Agreement to be given or made by the Company or by the holder
of any Right Certificate to or on the Rights Agent shall be sufficiently given
or made if sent by first-class mail, postage prepaid, addressed (until another
address is filed in writing with the Company) as follows:

                   American Stock Transfer & Trust Company
                   59 Maiden Lane, Plaza Level
                   New York, New York 10038

                   Attention: Corporate Trust Department

      Notices or demands authorized by this Agreement to be given or made by the
Company or the Rights Agent to the holder of any Right Certificate shall be
sufficiently given or made if sent by first-class mail, postage prepaid,
addressed to such holder at the address of such holder as shown on the registry
books of the Company.


                                       27
<PAGE>

      Section 27. Supplements and Amendments. The Company may from time to time,
and the Rights Agent shall, if the Company so directs, supplement or amend this
Agreement without the approval of any holders of Right Certificates in order to
cure any ambiguity, to correct or supplement any provision contained herein
which may be defective or inconsistent with any other provisions herein, or to
make any change to or delete any provision hereof or to adopt any other
provisions with respect to the Rights which the Company may deem necessary or
desirable; provided, however, that from and after such time as any Person
becomes an Acquiring Person, this Agreement shall not be amended or supplemented
in any manner which would adversely affect the interests of the holders of
Rights (other than an Acquiring Person and its Affiliates and Associates). Any
supplement or amendment authorized by this Section 27 will be evidenced by a
writing signed by the Company and the Rights Agent.

      Section 28. 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.

      Section 29. Benefits of this Agreement. Nothing in this Agreement shall be
construed to give to any person or entity other than the Company, the Rights
Agent and the registered holders of the Right Certificates (and, prior to the
Distribution Date, the Common Shares) any legal or equitable right, remedy or
claim under this Agreement; but this Agreement shall be for the sole and
exclusive benefit of the Company, the Rights Agent and the registered holders of
the Right Certificates (and, prior to the Distribution Date, the Common Shares).

      Section 30. Severability. If any term, provision, covenant or restriction
of this Agreement is held by a court of competent jurisdiction or other
authority to be invalid, void or unenforceable, the remainder of the terms,
provisions, covenants and restrictions of this Agreement shall remain in full
force and effect and shall in no way be affected, impaired or invalidated.

      Section 31. Governing Law. This Agreement and each Right Certificate
issued hereunder shall be deemed to be a contract made under the laws of the
State of Delaware 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.

      Section 32. 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 original, and all such counterparts shall together constitute but one and
the same instrument.

      Section 33. Descriptive Headings; Construction. Descriptive headings of
the several Sections of this Agreement are inserted for convenience only and
shall not control or affect the meaning or construction of any of the provisions
hereof. Whenever the content of this Agreement permits, the masculine gender
shall include the feminine and neuter genders, and reference to singular or
plural shall be interchangeable with the other.


                                       28
<PAGE>

      Section 34. Administration. The Board of Directors of the Company shall
have the exclusive power and authority to administer and interpret the
provisions of this Agreement and to exercise all rights and powers specifically
granted to the Board of Directors or the Company or as may be necessary,
desirable or advisable in the administration of this Agreement. All such
actions, calculations, determinations and interpretations which are done or made
by the Board of Directors in good faith shall be final, conclusive and binding
on the Company, the Rights Agent, the holders of the Rights and all other
parties and shall not subject the Board of Directors to any liability to the
holders of the Rights.

                  [Remainder of Page Left Intentionally Blank]


                                       29
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have caused this Rights Agreement
to be duly executed and their respective corporate seals to be hereunder affixed
and attested, all as of the day and year first above written.

Attest:                                 REPLIGEN CORPORATION

/s/ Barbara Burnim Day                  By: /s/ Walter Herlihy
-----------------------------------        -------------------------------------
Name: Barbara Burnim Day                   Name: Walter Herlihy
                                           Title: President, CEO


Attest:                                 AMERICAN STOCK TRANSFER & TRUST COMPANY

/s/ Susan Silber                        By: /s/ Herbert J. Lemmer
-----------------------------------        -------------------------------------
Name: Susan Silber                         Name: Herbert J. Lemmer
      Assistant Secretary                  Title: Vice President


                                       30
<PAGE>

                                                                       EXHIBIT A

                                      FORM

                                       of

                           CERTIFICATE OF DESIGNATION
                                       of

                  SERIES A JUNIOR PARTICIPATING PREFERRED STOCK
                                       of

                              REPLIGEN CORPORATION

                                   ----------

                         (Pursuant to Section 151 of the

                        Delaware General Corporation Law)

                                   ----------

      Repligen Corporation, a corporation organized and existing under the
General Corporation Law of the State of Delaware (hereinafter called the
"Corporation"), hereby certifies that the following resolution was adopted by
the Board of Directors of the Corporation as required by Section 151 of the
General Corporation Law at a meeting duly called and held on March 3, 2003:

      RESOLVED, that pursuant to the authority granted to and vested in the
Board of Directors of this Corporation (hereinafter called the "Board of
Directors" or the "Board") in accordance with the provisions of the Restated
Certificate of Incorporation of the Corporation (the "Certificate of
Incorporation"), the Board of Directors hereby creates a series of Preferred
Stock, par value $0.01 per share (the "Preferred Stock"), of the Corporation and
hereby states the designation and number of shares, and fixes the relative
rights, preferences, and limitations thereof as follows:

      Section 1. Designation and Amount. The shares of this series shall be
designated as "Series A Junior Participating Preferred Stock" (the "Series A
Preferred Stock") and the number of shares constituting the Series A Preferred
Stock shall be forty thousand (40,000). Such number of shares may be increased
or decreased by resolution of the Board of Directors; provided, that no decrease
shall reduce the number of shares of Series A Preferred Stock to a number less
than the number of shares then outstanding plus the number of shares reserved
for issuance upon the exercise of outstanding options, rights or warrants or
upon the conversion of any outstanding securities issued by the Corporation
convertible into Series A Preferred Stock.


                                      A-1
<PAGE>

      Section 2. Dividends and Distributions.

            (a) Subject to the rights of the holders of any shares of any series
of Preferred Stock (or any other stock) ranking prior and superior to the Series
A Preferred Stock with respect to dividends, the holders of shares of Series A
Preferred Stock shall be entitled to receive, when, as and if declared by the
Board of Directors out of funds legally available for the purpose, quarterly
dividends payable in cash on the last day of March, June, September and December
in each year (each such date being referred to herein as a "Quarterly Dividend
Payment Date"), commencing on the first Quarterly Dividend Payment Date after
the first issuance of a share or fraction of a share of Series A Preferred
Stock, in an amount (if any) per share of Series A Preferred Stock (rounded to
the nearest cent), subject to the provision for adjustment hereinafter set
forth, equal to 1,000 times the aggregate per share amount of all cash
dividends, and 1,000 times the aggregate per share amount (payable in kind) of
all non-cash dividends or other distributions, other than a dividend payable in
shares of Common Stock, par value $0.01 per share (the "Common Stock"), of the
Corporation or a subdivision of the outstanding shares of Common Stock (by
reclassification or otherwise), declared on the Common Stock since the
immediately preceding Quarterly Dividend Payment Date or, with respect to the
first Quarterly Dividend Payment Date, since the first issuance of any share or
fraction of a share of Series A Preferred Stock. In the event the Corporation
shall at any time declare or pay any dividend on the Common Stock payable in
shares of Common Stock, or effect a subdivision or combination or consolidation
of the outstanding shares of Common Stock (by reclassification or otherwise than
by payment of a dividend in shares of Common Stock) into a greater or lesser
number of shares of Common Stock, then in each such case the amount to which
holders of shares of Series A Preferred Stock were entitled immediately prior to
such event under the preceding sentence shall be adjusted by multiplying such
amount by a fraction, the numerator of which is the number of shares of Common
Stock outstanding immediately after such event and the denominator of which is
the number of shares of Common Stock that were outstanding immediately prior to
such event.

            (b) The Corporation shall declare a dividend or distribution on the
Series A Preferred Stock as provided in paragraph (A) of this Section
immediately after it declares a dividend or distribution on the Common Stock
(other than a dividend payable in shares of Common Stock).

            (c) Dividends due pursuant to paragraph (A) of this Section shall
begin to accrue and be cumulative on outstanding shares of Series A Preferred
Stock from the Quarterly Dividend Payment Date next preceding the date of issue
of such shares, unless the date of issue of such shares is prior to the record
date for the first Quarterly Dividend Payment Date, in which case dividends on
such shares shall begin to accrue from the date of issue of such shares, or
unless the date of issue is a Quarterly Dividend Payment Date or is a date after
the record date for the determination of holders of shares of Series A Preferred
Stock entitled to receive a quarterly dividend and before such Quarterly
Dividend Payment Date, in either of which events such dividends shall begin to
accrue and be cumulative from such Quarterly Dividend Payment Date. Accrued but
unpaid dividends shall not bear interest. Dividends paid on the shares of Series
A


                                      A-2
<PAGE>

Preferred Stock in an amount less than the total amount of such dividends at the
time accrued and payable on such shares shall be allocated pro rata on a
share-by-share basis among all such shares at the time outstanding. The Board of
Directors may fix a record date for the determination of holders of shares of
Series A Preferred Stock entitled to receive payment of a dividend or
distribution declared thereon, which record date shall be not more than 60 days
prior to the date fixed for the payment thereof.

      Section 3. Voting Rights. The holders of shares of Series A Preferred
Stock shall have the following voting rights:

            (a) Subject to the provision for adjustment hereinafter set forth,
each share of Series A Preferred Stock shall entitle the holder thereof to 1,000
votes on all matters submitted to a vote of the stockholders of the Corporation.
In the event the Corporation shall at any time declare or pay any dividend on
the Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise than by payment of a dividend in shares of Common
Stock) into a greater or lesser number of shares of Common Stock, then in each
such case the number of votes per share to which holders of shares of Series A
Preferred Stock were entitled immediately prior to such event shall be adjusted
by multiplying such number by a fraction, the numerator of which is the number
of shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

            (b) Except as otherwise provided the Certificate of Incorporation,
including any other Certificate of Designations creating a series of Preferred
Stock or any similar stock, or by law, the holders of shares of Series A
Preferred Stock and the holders of shares of Common Stock and any other capital
stock of the Corporation having general voting rights shall vote together as one
class on all matters submitted to a vote of stockholders of the Corporation.

            (c) Except as set forth herein, or as otherwise required by law,
holders of Series A Preferred Stock shall have no special voting rights and
their consent shall not be required (except to the extent they are entitled to
vote with holders of Common Stock as set forth herein) for taking any corporate
action. Without limiting the generality of the foregoing, the number of
authorized shares of Preferred Stock may be increased or decreased (but not
below the number of shares thereof then outstanding) by the affirmative vote of
the holders of a majority of the stock of the Corporation entitled to vote,
irrespective of the provisions of Section 242(b)(2) of the General Corporation
Law.

      Section 4. Certain Restrictions.

            (a) Whenever quarterly dividends or other dividends or distributions
payable on the Series A Preferred Stock as provided in Section 2 are in arrears,
thereafter and until all accrued and unpaid dividends and distributions, whether
or not declared, on shares of Series A Preferred Stock outstanding shall have
been paid in full, the Corporation shall not:


                                      A-3
<PAGE>

            (i) declare or pay dividends, or make any other distributions, on
any shares of stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series A Preferred Stock, other than dividends
on the Common Stock payable solely in additional shares of Common Stock;

            (ii) declare or pay dividends, or make any other distributions, on
any shares of stock ranking on a parity (either as to dividends or upon
liquidation, dissolution or winding up) with the Series A Preferred Stock,
except dividends paid ratably on the Series A Preferred Stock and all such
parity stock on which dividends are payable or in arrears in proportion to the
total amounts to which the holders of all such shares are then entitled; or

            (iii) redeem or purchase or otherwise acquire for consideration
shares of any stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series A Preferred Stock, provided that the
Corporation may at any time redeem, purchase or otherwise acquire shares of any
such junior stock in exchange for shares of any stock of the Corporation ranking
junior (as to dividends and upon dissolution, liquidation or winding up) to the
Series A Preferred Stock.

            (b) The Corporation shall not permit any subsidiary of the
Corporation to purchase or otherwise acquire for consideration any shares of
stock of the Corporation unless the Corporation could, under paragraph (A) of
this Section 4, purchase or otherwise acquire such shares at such time and in
such manner.

      Section 5. Reacquired Shares. Any shares of Series A Preferred Stock
purchased or otherwise acquired by the Corporation in any manner whatsoever
shall be retired and canceled promptly after the acquisition thereof. All such
shares shall upon their cancellation become authorized but unissued shares of
Preferred Stock and may be reissued as part of a new series of Preferred Stock
subject to the conditions and restrictions on issuance set forth herein or in
the Restated Certificate of Incorporation, including any Certificate of
Designations creating a series of Preferred Stock or any similar stock, or as
otherwise required by law.

      Section 6. Liquidation, Dissolution or Winding Up. Upon any liquidation,
dissolution or winding up of the Corporation the holders of shares of Series A
Preferred Stock shall be entitled to receive an aggregate amount per share of
Series A Preferred Stock, subject to the provision for adjustment hereinafter
set forth, equal to 1,000 times the aggregate amount to be distributed per share
to holders of shares of Common Stock plus an amount equal to any accrued and
unpaid dividends. In the event the Corporation shall at any time declare or pay
any dividend on the Common Stock payable in shares of Common Stock, or effect a
subdivision or combination or consolidation of the outstanding shares of Common
Stock (by reclassification or otherwise than by payment of a dividend in shares
of Common Stock) into a greater or lesser number of shares of Common Stock, then
in each such case the aggregate amount to which holders of shares of Series A
Preferred Stock were entitled immediately prior to such event under the
preceding sentence shall be adjusted by multiplying such amount by a fraction
the numerator of which is the number of shares of Common Stock outstanding
immediately after such event and the


                                      A-4
<PAGE>

denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

      Section 7. Consolidation, Merger, etc. In case the Corporation shall enter
into any consolidation, merger, combination 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 each share of
Series A Preferred Stock shall at the same time be similarly exchanged or
changed into an amount per share, subject to the provision for adjustment
hereinafter set forth, equal to 1,000 times the aggregate amount of stock,
securities, cash and/or any other property (payable in kind), as the case may
be, into which or for which each share of Common Stock is changed or exchanged.
In the event the Corporation shall at any time declare or pay any dividend on
the Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise than by payment of a dividend in shares of Common
Stock) into a greater or lesser number of shares of Common Stock, then in each
such case the amount set forth in the preceding sentence with respect to the
exchange or change of shares of Series A Preferred Stock shall be adjusted by
multiplying such amount by a fraction, the numerator of which is the number of
shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

      Section 8. Amendment. The Restated Certificate of Incorporation shall not
be amended in any manner, including in a merger or consolidation, which would
alter, change, or repeal the powers, preferences or special rights of the Series
A Preferred Stock so as to affect them adversely without the affirmative vote of
the holders of at least two-thirds of the outstanding shares of Series A
Preferred Stock, voting together as a single class.

      Section 9. Rank. The Series A Preferred Stock shall rank, with respect to
the payment of dividends and upon liquidation, dissolution and winding up,
junior to all series of Preferred Stock.

                  [Remainder of Page Left Intentionally Blank]


                                      A-5
<PAGE>

      IN WITNESS WHEREOF, this Certificate of Designation is executed on behalf
of the Corporation by its _______ this ______ day of March, 2003.

                                        REPLIGEN CORPORATION


                                        By: ____________________________________
                                            Name: ______________________________
                                            Title: _____________________________


                                      A-6
<PAGE>

                                                                       EXHIBIT B

Form of Right Certificate
Certificate No. R-_ _______ Rights

NOT EXERCISABLE AFTER MARCH 2, 2013 OR EARLIER IF REDEMPTION OR EXCHANGE OCCURS.
THE RIGHTS ARE SUBJECT TO REDEMPTION AT $0.001 PER RIGHT AND TO EXCHANGE ON THE
TERMS SET FORTH IN THE RIGHTS AGREEMENT. UNDER CERTAIN CIRCUMSTANCES, RIGHTS
THAT ARE OR WERE ACQUIRED OR BENEFICIALLY OWNED BY AN ACQUIRING PERSON OR ANY
ASSOCIATES OR AFFILIATES THEREOF (AS SUCH TERMS ARE DEFINED IN THE RIGHTS
AGREEMENT) OR ANY SUBSEQUENT HOLDER OF SUCH RIGHTS MAY BECOME NULL AND VOID.

                                Right Certificate
                              Repligen Corporation

      This certifies that _______________________, or registered assigns, is the
registered owner of the number of Rights set forth above, each of which entitles
the owner thereof, subject to the terms, provisions and conditions of the Rights
Agreement, dated as of March 3, 2003 (the "Rights Agreement"), between Repligen
Corporation, a Delaware corporation (the "Company"), and American Stock Transfer
& Trust Company (the "Rights Agent"), to purchase from the Company at any time
after the Distribution Date (as such term is defined in the Rights Agreement)
and prior to 5:00 P.M., Boston, Massachusetts time, on March 2, 2013, at the
principal office of the Rights Agent, or at the office of its successor as
Rights Agent, one one-thousandth of a fully paid non-assessable share of Series
A Junior Participating Preferred Stock, par value $0.01 per share (the
"Preferred Shares"), of the Company, at a purchase price of $50.00 per one
one-thousandth of a Preferred Share (the "Purchase Price"), upon presentation
and surrender of this Right Certificate with the certification and the Form of
Election to Purchase duly executed. The number of Rights evidenced by this Right
Certificate (and the number of one one-thousandths of a Preferred Share which
may be purchased upon exercise hereof) set forth above, and the Purchase Price
set forth above, are the number and Purchase Price as of March 3, 2003, based on
the Preferred Shares as constituted at such date. As provided in the Rights
Agreement, the Purchase Price and the number of one one-thousandths of a
Preferred Share which may be purchased upon the exercise of the Rights evidenced
by this Right Certificate are subject to modification and adjustment upon the
happening of certain events.

      From and after the occurrence of an event described in Section 11(a)(ii)
of the Rights Agreement, if the Rights evidenced by this Right Certificate are
or were at any time on or after the earlier of (x) the date of such event and
(y) the Distribution Date (as such term is defined in the Rights Agreement)
acquired or beneficially owned by an Acquiring Person or an Associate or
Affiliate of an Acquiring Person (as such terms are defined in the Rights
Agreement), such Rights shall become void, and any holder of such Rights shall
thereafter have no right to exercise such Rights.


                                      B-1
<PAGE>

      This Right 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 Right Certificates. Copies of
the Rights Agreement are on file at the principal executive offices of the
Company and the offices of the Rights Agent.

      This Right Certificate, with or without other Right Certificates, upon
surrender at the principal office of the Rights Agent, may be exchanged for
another Right Certificate or Right Certificates of like tenor and date
evidencing Rights entitling the holder to purchase a like aggregate number of
Preferred Shares as the Rights evidenced by the Right Certificate or Right
Certificates surrendered shall have entitled such holder to purchase. If this
Right Certificate shall be exercised in part, the holder shall be entitled to
receive upon surrender hereof another Right Certificate or Right Certificates
for the number of whole Rights not exercised.

      Subject to the provisions of the Rights Agreement, at the Company's
option, the Rights evidenced by this Certificate (i) may be redeemed by the
Company at a redemption price of $0.001 per Right or (ii) may be exchanged in
whole or in part for shares of the Company's Common Stock, par value $0.01 per
share, or Preferred Shares.

      No fractional Preferred Shares will be issued upon the exercise of any
Right or Rights evidenced hereby (other than fractions which are integral
multiples of one one-thousandth of a Preferred Share, which may, at the election
of the Company, be evidenced by depository receipts), but in lieu thereof a cash
payment will be made, as provided in the Rights Agreement.

      No holder of this Right Certificate shall be entitled to vote or receive
dividends or be deemed for any purpose the holder of the Preferred Shares or of
any other securities of the Company 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 Right or Rights evidenced by this Right Certificate shall have been
exercised as provided in the Rights Agreement.

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


                                      B-2
<PAGE>

      WITNESS the facsimile signature of the proper officers of the Company and
its corporate seal. Dated as of ____ __, 20__.

Attest:                                 REPLIGEN CORPORATION

________________________________        By: ____________________________________
                                            Name: ______________________________
Countersigned:                              Title: _____________________________


AMERICAN STOCK TRANSFER
& TRUST COMPANY

By: ____________________________
    Name: ______________________
    Title: _____________________
    Authorized Signatory


                                      B-3
<PAGE>

                    Form of Reverse Side of Right Certificate

                               FORM OF ASSIGNMENT

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

      FOR VALUE RECEIVED _________________________________ hereby sells, assigns
and transfers unto _____________________________________________________________
                  (Please print name and address of transferee)

this Right Certificate, together with all right, title and interest therein, and
does hereby irrevocably constitute and appoint ____________________________,
Attorney, to transfer the within Right Certificate on the books of the
within-named Company, with full power of substitution.

Dated: _____________ ___, _____


                                        ________________________________________
                                        Signature

Signature Guaranteed:

      Signatures must be guaranteed by an eligible guarantor institution (a
bank, stockbroker, savings and loan association or credit union with membership
in an approved signature guarantee medallion program) pursuant to Rule 17Ad-15
of the Securities Exchange Act of 1934.

                                   ----------

                                   CERTIFICATE

      The undersigned hereby certifies that the Rights evidenced by this Right
Certificate are not beneficially owned by an Acquiring Person or an Affiliate or
Associate thereof (as defined in the Rights Agreement).


                                        ________________________________________
                                        Signature

                                   ----------


                                      B-4
<PAGE>

               Form of Reverse Side of Right Certificate continued

                          FORM OF ELECTION TO PURCHASE

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

To Repligen Corporation:

      The undersigned hereby irrevocably elects to exercise ________________
Rights represented by this Right Certificate to purchase the number of one
one-thousandths of a share of Preferred Shares (or other securities) issuable
upon the exercise of such Rights and requests that certificates for such shares
be issued in the name of:

Please insert social security
or other identifying number

_________________________________________________________________
                  (Please print name and address)

_________________________________________________________________

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

Please insert social security
or other identifying number

_________________________________________________________________
                  (Please print name and address)

_________________________________________________________________

Dated: _____________ ___, _____


                                        ________________________________________
                                        Signature
                                        (Signature must conform in all respects
                                        to the name of the holder as specified
                                        on the face of this Right Certificate)

Signature Guaranteed:**


_______________________________
**Signatures must be guaranteed by an "Eligible Guarantor Institution" (with
membership in an approved signature guarantee medallion program) pursuant to
Rule 17Ad-15 of the Securities Exchange Act of 1934.


                                      B-5
<PAGE>

               Form of Reverse Side of Right Certificate continued

      The undersigned hereby certifies that the Rights evidenced by this Right
Certificate are not beneficially owned by an Acquiring Person or an Affiliate or
Associate thereof (as defined in the Rights Agreement).


                                        ________________________________________
                                        Signature

                                   ----------

                                     NOTICE

      The signature in the foregoing Forms of Assignment and Election must
conform to the name as written upon the face of this Right Certificate in every
particular, without alteration or enlargement or any change whatsoever.

      In the event the certification set forth above in the Form of Assignment
or the Form of Election to Purchase, as the case may be, is not completed, the
Company and the Rights Agent will deem the beneficial owner of the Rights
evidenced by this Right Certificate to be an Acquiring Person or an Affiliate or
Associate thereof (as defined in the Rights Agreement) and such Assignment or
Election to Purchase will not be honored.


                                      B-6
<PAGE>

                                                                       EXHIBIT C

                              REPLIGEN CORPORATION
                          SUMMARY OF RIGHTS TO PURCHASE
                                PREFERRED SHARES

      On March 3, 2003, the Board of Directors of Repligen Corporation (the
"Company") declared a dividend of one preferred share purchase right (a "Right")
for each outstanding share of common stock, par value $0.01 per share (the
"Common Shares") outstanding on March 17, 2003 (the "Record Date") to the
stockholders of record on that date. Each Right entitles the registered holder
to purchase from the Company one one-thousandth of a share of Series A Junior
Participating Preferred Stock, par value $0.01 per share (the "Preferred
Shares"), of the Company, at a price of $50.00 per one one-thousandth of a
Preferred Share (the "Purchase Price"), subject to adjustment. This summary
description and terms of the Rights set forth herein are qualified in their
entirety by that certain Rights Agreement (the "Rights Agreement") between the
Company and American Stock Transfer & Trust Company (the "Rights Agent") dated
as of March 3, 2003, which is hereby incorporated herein in its entirety by
reference.

      Until the earlier to occur of (i) the close of business on the tenth
calendar day after a public announcement or disclosure of facts that a person or
group of affiliated or associated persons (an "Acquiring Person") has acquired
beneficial ownership of 15% or, in the case of a Grandfathered Stockholder (as
such term is defined in the Rights Agreement) 20% or more of the outstanding
Common Shares or (ii) the tenth business day (or such later date as may be
determined by action of the Board of Directors prior to such time as any Person
becomes an Acquiring Person) following the commencement of, or the public
announcement of an intention to make, a tender or exchange offer, the
consummation of which would result in the beneficial ownership by a person or
group of 15% or, in the case of a Grandfathered Stockholder, 20% or more of such
outstanding Common Shares (the earlier of such dates being called the
"Distribution Date"), the Rights will be evidenced, with respect to any of the
Common Share certificates outstanding as of the Record Date, by such Common
Share certificate with a copy of this Summary of Rights attached thereto.

      The Rights Agreement provides that, until the Distribution Date, the
Rights will be transferred with and only with the Common Shares. Until the
Distribution Date (or earlier redemption or expiration of the Rights), new
Common Share certificates issued after the Record Date or upon transfer or new
issuance of Common Shares will contain a notation incorporating the Rights
Agreement by reference. Until the Distribution Date (or earlier redemption or
expiration of the Rights), the surrender for transfer of any certificates for
Common Shares outstanding as of the Record Date, even without such notation or a
copy of this Summary of Rights being attached thereto, will also constitute the
transfer of the Rights associated with the Common Shares represented by such
certificate. As soon as practicable following the Distribution Date, separate
certificates evidencing the Rights ("Right Certificates") will be


                                      C-1
<PAGE>

mailed to holders of record of the Common Shares as of the Close of Business on
the Distribution Date and such separate Right Certificates alone will evidence
the Rights.

      The Rights are not exercisable until the Distribution Date. The Rights
will expire on March 2, 2013 (the "Final Expiration Date"), unless the Final
Expiration Date is extended or unless the Rights are earlier redeemed by the
Company, in each case, as described below.

      The Purchase Price payable, and the number of Preferred Shares or other
securities or property issuable, upon exercise of the Rights are subject to
adjustment from time to time to prevent dilution (i) in the event of a stock
dividend on, or a subdivision, combination or reclassification of, the Preferred
Shares, (ii) upon the grant to holders of the Preferred Shares of certain rights
or warrants to subscribe for or purchase Preferred Shares at a price, or
securities convertible into Preferred Shares with a conversion price, less than
the then current market price of the Preferred Shares or (iii) upon the
distribution to holders of the Preferred Shares of evidences of indebtedness or
assets (excluding regular periodic cash dividends paid out of earnings or
retained earnings or dividends payable in Preferred Shares) or of subscription
rights or warrants (other than those referred to above).

      The number of outstanding Rights and the number of one one-thousandths of
a Preferred Share issuable upon exercise of each Right are also subject to
adjustment in the event of a stock split of the Common Shares or a stock
dividend on the Common Shares payable in Common Shares or subdivisions,
consolidations or combinations of the Common Shares occurring, in any such case,
prior to the Distribution Date.

      Preferred Shares purchasable upon exercise of the Rights will not be
redeemable. Each Preferred Share will be entitled to a quarterly dividend
payment of 1,000 times the dividend declared per Common Share. In the event of
liquidation, the holders of the Preferred Shares will be entitled to an
aggregate payment of 1,000 times the aggregate payment made per Common Share.
Each Preferred Share will have 1,000 votes, voting together with the Common
Shares. In the event of any merger, consolidation or other transaction in which
Common Shares are exchanged, each Preferred Share will be entitled to receive
1,000 times the amount received per Common Share. These rights are protected by
customary antidilution provisions.

      Because of the nature of the Preferred Shares' dividend, liquidation and
voting rights, the value of the one one-thousandth interest in a Preferred Share
purchasable upon exercise of each Right should approximate the value of one
Common Share.

      From and after the occurrence of an event described in Section 11(a)(ii)
of the Rights Agreement, if the Rights evidenced by the Right Certificate are or
were at any time on or after the earlier of (x) the date of such event and (y)
the Distribution Date (as such term is defined in the Rights Agreement) acquired
or beneficially owned by an Acquiring Person or an Associate or Affiliate of an
Acquiring Person (as such terms are defined in the Rights Agreement), such
Rights shall become void, and any holder of such Rights shall thereafter have no
right to exercise such Rights.


                                      C-2
<PAGE>

      In the event that, at any time after a Person becomes an Acquiring Person,
the Company is acquired in a merger or other business combination transaction or
50% or more of its consolidated assets or earning power are sold, proper
provision will be made so that each holder of a Right will thereafter have the
right to receive, upon the exercise thereof at the then current exercise price
of the Right, that number of shares of common stock of the acquiring company
which at the time of such transaction will have a market value of two times the
exercise price of the Right. In the event that any person becomes an Acquiring
Person, proper provision shall be made so that each holder of a Right, other
than Rights beneficially owned by the Acquiring Person and its Affiliates and
Associates (which will thereafter be void), will thereafter have the right to
receive upon exercise that number of Common Shares having a market value of two
times the exercise price of the Right. If the Company does not have sufficient
Common Shares to satisfy such obligation to issue Common Shares, or if the Board
of Directors so elects, the Company shall deliver upon payment of the exercise
price of a Right an amount of cash or securities equivalent in value to the
Common Shares issuable upon exercise of a Right; provided that, if the Company
fails to meet such obligation within 30 days following the later of (x) the
first occurrence of an event triggering the right to purchase Common Shares and
(y) the date on which the Company's right to redeem the Rights expires, the
Company must deliver, upon exercise of a Right but without requiring payment of
the exercise price then in effect, Common Shares (to the extent available) and
cash equal in value to the difference between the value of the Common Shares
otherwise issuable upon the exercise of a Right and the exercise price then in
effect. The Board of Directors may extend the 30-day period described above for
up to an additional 90 days to permit the taking of action that may be necessary
to authorize sufficient additional Common Shares to permit the issuance of
Common Shares upon the exercise in full of the Rights.

      At any time after any Person becomes an Acquiring Person and prior to the
acquisition by any person or group of a majority of the outstanding Common
Shares, the Board of Directors of the Company may exchange the Rights (other
than Rights owned by such person or group which have become void), in whole or
in part, at an exchange ratio of one Common Share per Right (subject to
adjustment).

      With certain exceptions, no adjustment in the Purchase Price will be
required until cumulative adjustments require an adjustment of at least 1% in
such Purchase Price. No fractional Preferred Shares will be issued (other than
fractions which are integral multiples of one one-thousandth of a Preferred
Share, which may, at the election of the Company, be evidenced by depository
receipts) and in lieu thereof, an adjustment in cash will be made based on the
market price of the Preferred Shares on the last trading day prior to the date
of exercise.

      At any time prior to the earlier of (i) the close of business on the tenth
calendar day after the time any Person becomes an Acquiring Person (or such
later date as may be determined by the Board of Directors in its sole
discretion), or the (ii) Final Expiration Date, the Board of Directors of the
Company may redeem the Rights in whole, but not in part, at a price of $0.001
per Right (the "Redemption Price"). The redemption of the Rights may be made
effective at such time, on such basis and with such conditions as the Board of
Directors in its sole discretion


                                      C-3
<PAGE>

may establish. Immediately upon any redemption of the Rights, the right to
exercise the Rights will terminate and the only right of the holders of Rights
will be to receive the Redemption Price.

      The terms of the Rights may be amended by the Board of Directors of the
Company without the consent of the holders of the Rights, except that from and
after such time as any person becomes an Acquiring Person no such amendment may
adversely affect the interests of the holders of the Rights (other than the
Acquiring Person and its Affiliates and Associates).

      Until a Right is exercised, the holder thereof, as such, will have no
rights as a stockholder of the Company, including, without limitation, the right
to vote or to receive dividends.

      A copy of the Agreement has been filed with the Securities and Exchange
Commission as an Exhibit to a Registration Statement on Form 8-A dated March 4,
2003. A copy of the Agreement is available free of charge from the Company.


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