Document:

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                                   EXHIBIT 4.7

                               INPUT/OUTPUT, INC.
                           2000 RESTRICTED STOCK PLAN

         The Input/Output, Inc. 2000 Restricted Stock Plan (hereinafter called
the "Plan") was adopted by the Board of Directors of Input/Output, Inc., a
Delaware corporation (hereinafter called the "Sponsoring Company"), effective
as of March 13, 2000.

                                    ARTICLE 1
                                     PURPOSE

         The purpose of the Plan is to attract and retain the services of key
management employees of the Company and its Subsidiaries and to provide such
persons with a proprietary interest in the Company through the granting of
restricted stock that will

                  (a)     increase the interest of such persons in the
                          Company's welfare;

                  (b)     furnish an incentive to such persons to continue
                          their services for the Company;

                  (c)     provide a means through which the Company may attract
                          able persons as employees; and

                  (d)     in instances where authorized by the Committee,
                          provide certain key employees additional incentives
                          to make substantial contributions to the Company's
                          growth measured by the attainment of performance
                          goals.

                                    ARTICLE 2
                                   DEFINITIONS

         For the purpose of the Plan, unless the context requires otherwise,
the following terms shall have the meanings indicated:

         2.1      "Award" means a grant of Restricted Stock under the Plan.

         2.2      "Award Agreement" means a written agreement between a
Participant and the Company which sets out the terms of the grant of an Award.

         2.3      "Board" means the board of directors of the Company.

         2.4      "Change of Control" means the occurrence of any of the
following events: (i) there shall be consummated any merger or consolidation
pursuant to which shares of the Company's Common Stock would be converted into
cash, securities or other property, or any sale, lease, exchange or other
disposition (excluding disposition by way of mortgage, pledge or
hypothecation), in one transaction or a series of related transactions, of all
or substantially all the assets of the Company (a "Business Combination"), in
each case unless, following such Business Combination, the holders of the
outstanding Common Stock of the Company immediately prior to such Business
Combination beneficially own, directly or indirectly, more than 51% of the
outstanding common stock or equivalent equity interests of the corporation or
entity resulting from such Business Combination (including, without
limitation, a corporation which as a result of such transaction owns the
Company or all or substantially all of the Company's assets either directly or
through one or more subsidiaries) in substantially the same proportions as
their ownership, immediately prior to such Business Combination, of the
outstanding common stock, (ii) the stockholders of the

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Company approve any plan or proposal for the complete liquidation or
dissolution of the Company, (iii) any "person" (as such term is defined in
Section 3(a)(9) or Section 13(d)(3) under the Securities Exchange Act of 1934
(the "1934 Act") or any "group" (as such term is used in Rule 13d-5
promulgated under the 1934 Act) other than an Employer or a successor of an
Employer, or any employee benefit plan of an Employer (including such plan's
trustee), becomes a beneficial owner for purposes of Rule 13d-3 promulgated
under the 1934 Act, directly or indirectly, of securities of the Company
representing 40% or more of the Company's then outstanding common securities
having the right to vote in the election of directors, or (iv) during any
period of two consecutive years, individuals who, at the beginning of such
period constituted the entire Board, cease for any reason (other than death)
to constitute a majority of the directors, unless the elections, or the
nomination for election by the Company's stockholders, of each new director
was approved by a vote of at least a majority of the directors then still in
office who were directors at the beginning of the period. For purposes of this
definition, the term "Company" shall include any successor or assignee of such
corporation, which successor or assignee assumes such status other than
pursuant to an event or occurrence constituting a "Change of Control."

         2.5      "Code" means the Internal Revenue Code of 1986, as amended.

         2.6      "Committee" means the committee appointed or designated by
the Board to administer the Plan in accordance with ARTICLE 3 of this Plan.

         2.7      "Common Stock" means the common stock, par value $0.01 per
share, which the Company is currently authorized to issue or may in the future
be authorized to issue.

         2.8      "Date of Grant" means the effective date on which an Award
is made to a Participant as set forth in the applicable Award Agreement.

         2.9      "Employee" means common law employee (as defined in
accordance with the Regulations and Revenue Rulings then applicable under
Section 3401(c) of the Code) of the Company or any Subsidiary of the Company.

         2.10     "Employer" shall mean the Company or any affiliated company
or Subsidiary of the Company that adopts the Plan.

         2.11     "Fair Market Value" of a share of Common Stock is the
closing sales price per share on the New York Stock Exchange Consolidated
Tape, or such reporting service as the Committee may select, on the
appropriate date, or in the absence of reported sales on such day, the most
recent previous day for which sales were reported.

         2.12     "Participant" shall mean an Employee of the Company or a
Subsidiary to whom an Award is granted under this Plan.

         2.13     "Plan" means this Input/Output, Inc. 2000 Restricted Stock
Plan, as amended from time to time.

         2.14     "Restricted Stock" means shares of Common Stock issued or
transferred to a Participant pursuant to this Plan which are subject to
restrictions or limitations set forth in this Plan and in a related Award
Agreement.

         2.15     "Restriction Period" shall have the meaning set forth in
SECTION 6.5(a) hereof.

         2.16     "Retirement" means any Termination of Service solely due to
retirement after attaining age 65, or permitted early retirement as determined
by the Committee.

         2.17     "Subsidiary" means (i) any corporation in an unbroken chain
of corporations beginning with the Company, if each of the corporations other
than the last corporation in the unbroken chain owns stock possessing a

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majority of the total combined voting power of all classes of stock in one of
the other corporations in the chain, (ii) any limited partnership, if the
Company or any corporation described in item (i) above owns a majority of the
general partner interests and a majority of the limited partners' interests
entitled to vote on the removal and replacement of the general partner, and
(iii) any general partnership or limited liability company, if the partners or
members thereof are composed only of the Company, any corporation listed in
item (i) above or any limited partnership listed in item (ii) above.
"Subsidiaries" means more than one of any such corporations, limited
partnerships, general partnerships or limited liability companies.

         2.18     "Termination of Service" occurs when a Participant who is an
Employee of the Company or any Subsidiary shall cease to serve as an Employee
of the Company and its Subsidiaries, for any reason.

         2.19     "Total and Permanent Disability" means the Participant's
total and permanent disability, as that term is described in Section 22(e) of
the Code.

                                    ARTICLE 3
                                 ADMINISTRATION

         The Plan shall be administered by the Compensation Committee of the
Board or another committee appointed by the Board (the "Committee"). The
Committee shall consist of not fewer than two persons. Any member of the
Committee may be removed at any time, with or without cause, by resolution of
the Board. Any vacancy occurring in the membership of the Committee may be
filled by appointment by the Board.

         The Committee shall select one of its members to act as its Chairman.
A majority of the Committee shall constitute a quorum, and the act of a
majority of the members of the Committee present at a meeting at which a
quorum is present shall be the act of the Committee.

         The Committee shall determine and designate from time to time the
eligible persons to whom Awards will be granted and shall set forth in each
related Award Agreement, the Date of Grant and such other terms, provisions,
limitations, and performance requirements (if any), as are approved by the
Committee, but not inconsistent with the Plan.

         The Committee, in its discretion, shall (i) interpret the Plan, (ii)
prescribe, amend, and rescind any rules and regulations necessary or
appropriate for the administration of the Plan, and (iii) make such other
determinations and take such other action as it deems necessary or advisable
in the administration of the Plan. Any interpretation, determination, or other
action made or taken by the Committee shall be final, binding, and conclusive
on all interested parties.

                                    ARTICLE 4
                                   ELIGIBILITY

         Employees who are eligible to participate in the Plan (including an
Employee who is also a director or an officer) are those Employees whom the
Committee determines are key Employees. The Committee, upon its own action,
may grant, but shall not be required to grant, an Award to any Employee or
potential Employee of the Company or any Subsidiary. Awards may be granted by
the Committee at any time and from time to time to new Participants, or to
existing Participants, or to a greater or lesser number of Participants, and
may include or exclude previous Participants, as the Committee shall
determine. Except as required by this Plan, all Awards shall not be required
to contain the same or similar provisions. The Committee's determinations
under the Plan (including without limitation determinations of which Employees
or potential Employees, if any, are to receive Awards, the form, amount and
timing

                                     -3-

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of such Awards, the terms and provisions of such Awards and the agreements
evidencing same) need not be uniform and may be made by it selectively among
Employees who receive, or are eligible to receive, Awards under the Plan.

                                    ARTICLE 5
                             SHARES SUBJECT TO PLAN

         Subject to adjustment as provided in ARTICLES 9 AND 10, the maximum
number of shares of Common Stock that may be delivered pursuant to Awards
granted under the Plan is (a) Two Hundred Thousand (200,000) shares; plus (b)
any shares of Common Stock previously subject to Awards which are forfeited,
terminated, settled in cash in lieu of Common Stock, or exchanged for other
awards that do not involve Common Stock. Shares to be issued or delivered may
be made available from authorized but unissued Common Stock, Common Stock held
by the Company in its treasury, or Common Stock purchased by the Company on
the open market or otherwise; provided however, that shares to be delivered
with regards to the initial grant of Awards under this Plan shall be made
available only from Company treasury shares or Common Stock repurchased by the
Company.

                                    ARTICLE 6
                                 GRANT OF AWARDS

         6.1      IN GENERAL. The grant of an Award shall be authorized by the
Committee and shall be evidenced by an Award Agreement setting forth the Award
being granted, the total number of shares of Common Stock subject to the
Award, the Date of Grant, and such other terms, provisions, limitations, and
performance objectives, as are approved by the Committee, but not inconsistent
with the Plan. The Company shall execute an Award Agreement with a Participant
after the Committee approves the issuance of an Award. Any Award granted
pursuant to this Plan must be granted within ten (10) years of the date of
adoption of this Plan. The grant of an Award to a Participant shall not be
deemed either to entitle the Participant to, or to disqualify the Participant
from, receipt of any other Award under the Plan.

         If the Committee establishes a purchase price for an Award, the
Participant must accept such Award within a period of 30 days (or such shorter
period as the Committee may specify) after the Date of Grant by executing the
applicable Award Agreement and paying such purchase price.

         6.2      MAXIMUM INDIVIDUAL GRANTS. No Participant may receive,
during any fiscal year of the Company, Awards covering an aggregate of more
than Fifty Thousand (50,000) shares of Common Stock.

         6.3      AWARD AGREEMENT. The Committee shall set forth in the
related Award Agreement: (i) the number of shares of Common Stock awarded,
(ii) the price, if any, to be paid by the Participant for such Restricted
Stock, (iii) the time or times within which such Award may be subject to
forfeiture, (iv) specified performance goals (if applicable) of the Company, a
Subsidiary, any division thereof or any group of Employees of the Company, or
any other criteria, which the Committee determines must be met in order to
remove any restrictions (including vesting) on such Award, and (v) all other
terms, limitations, restrictions, and conditions of the Restricted Stock,
which shall be consistent with this Plan. The provisions of a Restricted Stock
Award need not be the same with respect to each Participant.

         6.4      CUSTODY OF SHARES; LEGEND ON SHARES. Each Participant who is
awarded Restricted Stock shall be issued a stock certificate or certificates
in respect of such shares of Common Stock. Such certificate(s) shall be
registered in the name of the Participant, and shall bear an appropriate
legend referring to the terms, conditions, and restrictions applicable to such
Restricted Stock, substantially as provided in SECTION 13.8 of the Plan. The
Committee may require that the stock certificates evidencing shares of
Restricted Stock be held in custody by the Company until the restrictions
thereon shall have lapsed, and that the Participant deliver to the Committee a
stock power or stock powers, endorsed in blank, relating to the shares of
Restricted Stock.

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         6.5      RESTRICTIONS AND CONDITIONS. Shares of Restricted Stock
shall be subject to the following restrictions and conditions:

                  (a) NO DISPOSITION DURING RESTRICTION PERIOD. Subject to the
         other provisions of this Plan and the terms of the particular Award
         Agreements, during such period as may be determined by the Committee
         commencing on the Date of Grant (the "Restriction Period"), the
         Participant shall not be permitted to sell, transfer, pledge, assign,
         or otherwise dispose of shares of Restricted Stock. The Restriction
         Period for shares of Restricted Stock shall commence on the Date of
         Grant of such shares and, subject to ARTICLE 10 of the Plan, shall
         expire upon satisfaction of the conditions set forth in the Award
         Agreement; such conditions may provide for vesting based on (i)
         length of continuous service, (ii) achievement of specific business
         objectives, (iii) increases in specified indices, (iv) attainment of
         specified growth rates, or (v) other comparable measurements of
         Company performance (or that of any Subsidiary or division thereof),
         as may be determined by the Committee in its sole discretion. If the
         Committee imposes conditions upon vesting, then subsequent to the
         Date of Grant, the Committee may, in its sole discretion, accelerate
         the date on which all or any portion of the Award may be vested.

                  (b) RIGHTS DURING RESTRICTION PERIOD. Except as provided in
         paragraph (a) above, the Participant shall have, with respect to his
         or her Restricted Stock, all of the rights of a stockholder of the
         Company, including the right to vote the shares, and the right to
         receive any dividends thereon.

                  (c) LAPSE OF RESTRICTIONS. Certificates for shares of Common
         Stock free of restriction under this Plan shall be delivered to the
         Participant promptly after, and only after, the particular Restriction
         Period shall expire as a result of satisfaction of the conditions set
         forth in the Award Agreement.

                  (d) FORFEITURE. Subject to the provisions of the particular
         Award Agreement, upon Termination of Service for any reason other
         than the Participant's death, Total and Permanent Disability, or
         Retirement during the Restriction Period, the nonvested shares of
         Restricted Stock shall be forfeited by the Participant. In addition,
         an Award Agreement may provide for forfeiture of shares of Restricted
         Stock upon the occurrence of other events, including failure to
         achieve certain goals or objectives during a specified period of
         time. In the event a Participant has paid any consideration to the
         Company for such forfeited Restricted Stock, the Company shall, as
         soon as practicable after the event causing forfeiture (but in any
         event within five (5) business days), pay to the Participant, in
         cash, an amount equal to the total consideration paid by the
         Participant for such forfeited shares. Upon any forfeiture, all
         rights of a Participant with respect to the forfeited shares of the
         Restricted Stock shall cease and terminate, without any further
         obligation on the part of the Company. Certificates for the shares of
         Common Stock forfeited under the provisions of the Plan and the
         applicable Award Agreement shall be promptly returned to the Company
         by the forfeiting Participant. Each Award Agreement shall require
         that (i) each Participant, by his or her acceptance of Restricted
         Stock, irrevocably grants to the Company a power of attorney to
         transfer to the Company any shares so forfeited, and agrees to
         execute any documents requested by the Company in connection with
         such forfeiture and transfer, and (ii) such provisions regarding
         returns and transfers of stock certificates with respect to forfeited
         shares of Common Stock shall be specifically performable by the
         Company in a court of equity or law.

                                    ARTICLE 7
                           AMENDMENT OR DISCONTINUANCE

         Subject to the limitations set forth in this ARTICLE 7, the Board may
at any time and from time to time, without the consent of the Participants,
alter, amend, revise, suspend, or discontinue the Plan in whole or in part.
Any such amendment shall, to the extent deemed necessary or advisable by the
Committee, be applicable to any outstanding Awards theretofore granted under
the Plan, notwithstanding any contrary provisions contained in any Award
Agreement. In the event of any such amendment to the Plan, the holder of any
Award outstanding under the Plan

                                     -5-
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shall, upon request of the Committee and as a condition to the vesting
thereof, execute a conforming amendment to his applicable Award Agreement in
the form prescribed by the Committee. Notwithstanding anything contained in
this Plan to the contrary, unless required by law, no action contemplated or
permitted by this ARTICLE 7 shall adversely affect any rights of Participants
or obligations of the Company to Participants with respect to any Award
theretofore granted under the Plan without the consent of the affected
Participant.

                                    ARTICLE 8
                                      TERM

         The Plan shall be effective from the date that this Plan is approved
by the Board. Unless sooner terminated by action of the Board, the Plan will
terminate on March 13, 2010, but Awards granted before that date will continue
to be effective in accordance with their terms and conditions.

                                    ARTICLE 9
                               CAPITAL ADJUSTMENTS

         If at any time while the Plan is in effect, or Awards are
outstanding, there shall be any increase or decrease in the number of issued
and outstanding shares of Common Stock resulting from (a) the declaration or
payment of a stock dividend, (b) any recapitalization resulting in a stock
split-up, combination, or exchange of shares of Common Stock, or (c) other
increase or decrease in such shares of Common Stock effected without receipt
of any consideration by the Company, then and in such event:

                  (i) An appropriate adjustment shall be made in the maximum
         number of shares of Common Stock then subject to being awarded under
         the Plan and in the maximum number of shares of Common Stock that may
         be awarded to a Participant to the end that the same proportion of the
         Company's issued and outstanding shares of Common Stock shall continue
         to be subject to being so awarded; and

                  (ii) Appropriate adjustments shall be made in the number of
         outstanding shares of Restricted Stock with respect to which the
         applicable Restriction Period has not expired prior to any such
         change.

         Except as otherwise expressly provided herein, the issuance by the
Company of shares of its capital stock of any class, or securities convertible
into shares of capital stock of any class, either in connection with direct
sale or upon the exercise of rights, options, or warrants to subscribe
therefor, or upon conversion of shares or obligations of the Company
convertible into such shares or other securities, shall not affect, and no
adjustment by reason thereof shall be made with respect to, the number of
outstanding shares of Restricted Stock.

         Upon the occurrence of each event requiring an adjustment with
respect to any Award, the Company shall mail to each affected Participant its
computation of such adjustment which shall be conclusive and shall be binding
upon each such Participant.

                                   ARTICLE 10
                          RECAPITALIZATION, MERGER AND
                        CONSOLIDATION; CHANGE IN CONTROL

         10.1     RIGHT OF THE COMPANY. The existence of this Plan and Awards
granted hereunder shall not affect in any way the right or power of the
Company or its stockholders to make or authorize any or all adjustments,
recapitalizations, reorganizations, or other changes in the Company's capital
structure and its business, or any merger or consolidation of the Company, or
any issue of bonds, debentures, preferred or preference stocks ranking prior
to or

                                     -6-

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otherwise affecting the Common Stock or the rights thereof (or any rights,
options, or warrants to purchase same), or the dissolution or liquidation of
the Company, or any sale or transfer of all or any part of its assets or
business, or any other corporate act or proceeding, whether of a similar
character or otherwise.

         10.2     MERGER, CONSOLIDATION IF THE COMPANY IS SURVIVOR. Subject to
any required action by the stockholders (and except as otherwise provided in
SECTION 10.3 below), if the Company shall be the surviving or resulting
corporation in any merger, consolidation or share exchange, any Award granted
hereunder shall pertain to and apply to the securities or rights (including
cash, property, or assets) to which a holder of the number of shares of Common
Stock subject to the Award would have been entitled.

         10.3     MERGER, CONSOLIDATION IF THE COMPANY IS NOT SURVIVOR. In the
event of any merger, consolidation or share exchange pursuant to which the
Company is not the surviving or resulting corporation, (or the Company is the
surviving entity but the Common Stock of the Company is exchanged for cash,
property, securities or other consideration of or from any other entity) there
shall be substituted for each share of Common Stock subject to the unexercised
portions of such outstanding Awards, (i) that number of shares of each class
of stock or other securities or that amount of cash, property, or assets of
the surviving, resulting or consolidated entity which were distributed or
distributable to the stockholders of the Company in respect of each share of
Common Stock held by them, or (ii) such number of shares of stock, or other
securities, or such amount of cash, property or assets (or any combination
thereof) as proportionate in value as reasonably practicable to the
consideration distributed or distributable to the stockholders of the Company
with respect to each share of Common Stock held by them.

         10.4     CHANGE OF CONTROL. In the event of a Change of Control, the
acceleration of vesting of nonvested shares of Restricted Stock and the
expiration of the Restriction Period(s) with respect thereto shall be governed
by the provisions of the applicable Award Agreement.

                                   ARTICLE 11
                           LIQUIDATION OR DISSOLUTION

         In case the Company shall, at any time while any Award under this
Plan shall be in force and its Restriction Period remains unexpired, (i) sell
all or substantially all of its property, or (ii) dissolve, liquidate, or wind
up its affairs, then each Participant shall be thereafter entitled to receive,
in lieu of each share of Common Stock of the Company which such Participant
would have been entitled to receive under the Award, the same kind and amount
of any securities or assets as may be issuable, distributable, or payable upon
any such sale, dissolution, liquidation, or winding up with respect to each
share of Common Stock of the Company.

                                   ARTICLE 12
                           AWARDS IN SUBSTITUTION FOR
                      AWARDS GRANTED BY OTHER CORPORATIONS

         Awards may be granted under the Plan from time to time in
substitution for similar instruments held by employees of a corporation who
become or are about to become key Employees of the Company or any Subsidiary
as a result of a merger or consolidation of the employing corporation with the
Company or the acquisition by the Company of stock of the employing
corporation. The terms and conditions of the substitute Awards so granted may
vary from the terms and conditions set forth in this Plan to such extent as
the Committee at the time of grant may deem appropriate to conform, in whole
or in part, to the provisions of the Awards in substitution for which they are
granted.

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                                   ARTICLE 13
                            MISCELLANEOUS PROVISIONS

         13.1     INVESTMENT INTENT. The Company may require that there be
presented to and filed with it by any Participant under the Plan, such
evidence as it may deem necessary to establish that the Award granted or the
shares of Common Stock to be transferred to the Participants are being
acquired for investment and not with a view to their distribution.

         13.2     NO RIGHT TO CONTINUED EMPLOYMENT. Neither the Plan nor any
Award granted under the Plan shall confer upon any Participant any right with
respect to continuance of employment by the Company or any Subsidiary.

         13.3     INDEMNIFICATION OF BOARD AND COMMITTEE. No member of the
Board or the Committee, nor any officer or Employee of the Company acting on
behalf of the Board or the Committee, shall be personally liable for any
action, determination, or interpretation taken or made in good faith with
respect to the Plan, and all members of the Board or the Committee, and each
officer or employee of the Company acting on their behalf shall, to the extent
permitted by law, be fully indemnified and protected by the Company in respect
of any such action, determination, or interpretation.

         13.4     EFFECT OF THE PLAN. Neither the adoption of this Plan nor
any action of the Board or the Committee shall be deemed to give any person
any right to be granted an Award or any other rights except as may be
evidenced by an Award Agreement, or any amendment thereto, duly authorized by
the Committee and executed on behalf of the Company, and then only to the
extent and upon the terms and conditions expressly set forth therein.

         13.5     COMPLIANCE WITH OTHER LAWS AND REGULATIONS. Notwithstanding
anything contained herein to the contrary, the Company shall not be required
to issue or deliver shares of Common Stock under any Award if the issuance or
delivery thereof would constitute a violation by the Participant or the
Company of any provisions of any law or regulation of any governmental
authority or the rules of any national securities exchange or inter-dealer
quotation system or other forum in which shares of Common Stock are quoted or
traded; and, as a condition of any sale or issuance of shares of Common Stock
under an Award, the Committee may require such agreements or undertakings, if
any, as the Committee may deem necessary or advisable to assure compliance
with any such law or regulation. The Plan, the grant of Awards hereunder, and
the obligation of the Company to deliver shares of Common Stock, shall be
subject to all applicable federal and state laws, rules and regulations and to
such approvals by any government or regulatory agency as may be required.

         13.6     TAX REQUIREMENTS. The Company shall have the right to deduct
from all amounts hereunder paid in cash or other form, any Federal, state, or
local taxes required by law to be withheld with respect to such payments. The
Participant receiving shares of Common Stock issued under the Plan shall be
required to pay the Company the amount of any taxes which the Company is
required to withhold with respect to such shares of Common Stock.

         13.7     USE OF PROCEEDS. Proceeds from any sale of shares of Common
Stock pursuant to Awards granted under this Plan shall constitute general
funds of the Company.

         13.8     LEGEND. Each certificate representing shares of Restricted
Stock issued to a Participant shall bear the following legend, or a similar
legend deemed by the Company to constitute an appropriate notice of the
provisions hereof (any such certificate not having such legend shall be
surrendered upon demand by the Company and so endorsed):

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<PAGE>

                 On the face of the certificate:

                 "Transfer of this stock is restricted in accordance with
                 conditions printed on the reverse of this certificate."

                 On the reverse:

                 "The shares of stock evidenced by this certificate are subject
                 to and transferrable only in accordance with the terms of the
                 Input/Output, Inc. 2000 Restricted Stock Plan, a copy of which
                 is on file at the principal executive offices of the Company
                 in Stafford, Texas. No transfer or pledge of the shares
                 evidenced hereby may be made except in accordance with and
                 subject to the provisions of said Plan. By acceptance of this
                 certificate, any holder, transferee or pledgee hereof agrees
                 to be bound by all of the provisions of said Plan."

         The following legend shall be inserted on each certificate evidencing
Common Stock issued under the Plan if the shares were not issued in a
transaction registered under the applicable federal and state securities laws:

                 "Shares of stock represented by this certificate have been
                 acquired by the holder for investment and not for resale,
                 transfer or distribution, have been issued pursuant to
                 exemptions from the registration requirements of applicable
                 state and federal securities laws, and may not be offered for
                 sale, sold or transferred other than pursuant to effective
                 registration under such laws, or in transactions otherwise in
                 compliance with such laws, and upon evidence satisfactory to
                 the Company of compliance with such laws, as to which the
                 Company may rely upon an opinion of counsel satisfactory to
                 the Company."

         A copy of this Plan shall be kept on file in the principal executive
offices of the Company in Stafford, Texas.

         IN WITNESS WHEREOF, the Company has caused this instrument to be
executed pursuant to action taken by the Board.

                                            INPUT/OUTPUT, INC.

                                            By:
                                               --------------------------------
                                                 Name:
                                                      -------------------------
                                                 Title:
                                                       ------------------------

                                     -9-<PAGE>

THIS WARRANT HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, OR ANY APPLICABLE STATE SECURITIES LAWS, AND MAY NOT BE SOLD OR
TRANSFERRED UNLESS SUCH SALE OR TRANSFER IS IN ACCORDANCE WITH THE REGISTRATION
REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS OR SOME OTHER EXEMPTION FROM THE
REGISTRATION REQUIREMENTS OF SUCH ACT AND APPLICABLE LAWS IS AVAILABLE WITH
RESPECT THERETO.

                          COMMON STOCK PURCHASE WARRANT

Warrant No. __                                        Number of Shares: 129,946
                              REPLIGEN CORPORATION

                            Void after March 9, 2005

         1. ISSUANCE. This Warrant is issued to Paramount Capital, Inc.
("Paramount") on this 9th day of March, 2000 (the "Original Issue Date") by
RepliGen Corporation, a Delaware corporation (hereinafter with its successors
called the "Company"), pursuant to a certain Finders Agreement dated as of March
8, 2000 by and between Paramount and the Company.

         2. PURCHASE PRICE; NUMBER OF SHARES. Subject to the terms and
conditions hereinafter set forth, the registered holder of this Warrant (the
"Holder"), commencing on September 9, 2000, is entitled upon surrender of this
Warrant with the subscription form annexed hereto duly executed, at the office
of the Company, 117 Fourth Avenue, Needham, MA 02494, or such other office as
the Company shall notify the Holder of in writing, to purchase from the Company
at a price per share of $9.49 (the "Purchase Price"), one hundred twenty-nine
thousand nine hundred forty-six (129,946) fully paid and nonassessable shares of
Common Stock, $.01 par value per share, of the Company (the "Common Stock").
Until such time as this Warrant is exercised in full or expires, the Purchase
Price and the securities issuable upon exercise of this Warrant are subject to
adjustment as hereinafter provided.

         3. PAYMENT OF PURCHASE PRICE. The Purchase Price may be paid (i) in
cash or by check, (ii) by the surrender by the Holder to the Company of any
promissory notes or other obligations issued by the Company, with all such notes
and obligations so surrendered being credited against the Purchase Price in an
amount equal to the principal amount thereof plus accrued interest to the date
of surrender, (iii) through delivery by the Holder to the Company of other
securities issued by the Company, with such securities being credited against
the Purchase Price in an amount equal to the fair market value thereof, as
determined in good faith by the Board of Directors of the Company (the "Board"),
or (iv) by any combination of the foregoing. The Board shall promptly respond in
writing to an inquiry by the Holder as to the fair market

<PAGE>

                                      -2-

value of any securities  the Holder may wish to deliver to the Company  pursuant
to clause (iii) above.

         4. NET ISSUE ELECTION. The Holder may elect to receive, without the
payment by the Holder of any additional consideration, shares equal to the value
of this Warrant or any portion hereof by the surrender of this Warrant or such
portion to the Company, with the net issue election notice annexed hereto duly
executed, at the office of the Company. Thereupon, the Company shall issue to
the Holder such number of fully paid and nonassessable shares of Common Stock as
is computed using the following formula:

                                   X = Y (A-B)
                                       ------
                                        A

where

                           X = the number of shares to be issued to the Holder
pursuant to this Section 4.

                           Y = the number of shares covered by this Warrant in
                  respect of which the net issue election is made pursuant to
                  this Section 4.

                           A = the fair market value of one share of Common
                  Stock, which shall be equal to the average closing price on
                  the Nasdaq National Market of the Common Stock over the ten
                  (10) day period prior to the date the net issue election is
                  made pursuant to this Section 4.

                           B = the Purchase Price in effect under this Warrant
                  at the time the net issue election is made pursuant to this
                  Section 4.

The Board shall promptly respond in writing to an inquiry by the Holder as to
the fair market value of one share of Common Stock.

         5. PARTIAL EXERCISE. This Warrant may be exercised in part, and the
Holder shall be entitled to receive a new warrant, which shall be dated as of
the date of this Warrant, covering the number of shares in respect of which this
Warrant shall not have been exercised.

         6. ISSUANCE DATE. The person or persons in whose name or names any
certificate representing shares of Common Stock is issued hereunder shall be
deemed to have become the holder of record of the shares represented thereby as
at the close of business on the date this Warrant is exercised with respect to
such shares, whether or not the transfer books of the Company shall be closed.

         7. EXPIRATION DATE. This Warrant shall expire at the close of business
on March 9, 2005, and shall be void thereafter.

<PAGE>

                                      -3-

         8. RESERVED SHARES; VALID ISSUANCE. The Company covenants that it will
at all times from and after the date hereof reserve and keep available such
number of its authorized shares of Common Stock, free from all preemptive or
similar rights therein, as will be sufficient to permit the exercise of this
Warrant in full. The Company further covenants that such shares as may be issued
pursuant to the exercise of this Warrant will, upon issuance, be duly and
validly issued, fully paid and nonassessable and free from all taxes, liens and
charges with respect to the issuance thereof other than those caused or suffered
by the Holder hereof.

         9. DIVIDENDS. If after the Original Issue Date the Company shall
subdivide the Common Stock, by split-up or otherwise, or combine the Common
Stock, or issue additional shares of Common Stock in payment of a stock dividend
on the Common Stock, the number of shares issuable on the exercise of this
Warrant shall forthwith be proportionately increased in the case of a
subdivision or stock dividend, or proportionately decreased in the case of a
combination, and the Purchase Price shall forthwith be proportionately decreased
in the case of a subdivision or stock dividend, or proportionately increased in
the case of a combination.

         10. MERGERS AND RECLASSIFICATIONS. If after the Original Issue Date
there shall be any reclassification, capital reorganization or change of the
Common Stock (other than as a result of a subdivision, combination or stock
dividend provided for in Section 9 hereof), or any consolidation of the Company
with, or merger of the Company into, another corporation or other business
organization (other than a consolidation or merger in which the Company is the
continuing corporation and which does not result in any reclassification or
change of the outstanding Common Stock), or any sale or conveyance to another
corporation or other business organization of all or substantially all of the
assets of the Company, then, as a condition of such reclassification,
reorganization, change, consolidation, merger, sale or conveyance, lawful
provisions shall be made, and duly executed documents evidencing the same from
the Company or its successor shall be delivered to the Holder, so that the
Holder shall thereafter have the right to purchase, at a total price not to
exceed that payable upon the exercise of this Warrant in full, the kind and
amount of shares of stock and other securities and property receivable upon such
reclassification, reorganization, change, consolidation, merger, sale or
conveyance by a holder of the number of shares of Common Stock which might have
been purchased by the Holder immediately prior to such reclassification,
reorganization, change, consolidation, merger, sale or conveyance, and in any
such case appropriate provisions shall be made with respect to the rights and
interest of the Holder to the end that the provisions hereof (including without
limitation, provisions for the adjustment of the Purchase Price and the number
of shares issuable hereunder) shall thereafter be applicable in relation to any
shares of stock or other securities and property thereafter deliverable upon
exercise hereof.

         11. PURCHASE PRICE ADJUSTMENTS. If and whenever after the Original
Issue Date, but prior to March 9, 2001, the Company shall issue or sell any
shares of its Common Stock for a consideration per share less than the average
closing bid price for the five (5) days preceding any such issuance (the "Bid
Price"), and/or the Company shall issue or sell any securities convertible into
or exercisable for shares of its Common Stock for a consideration per share less
than the Bid Price on the date of such issue or sale, except in all instances
for the exercise of any options or warrants outstanding on the Original Issue
Date, or upon the grant or exercise of any options or

<PAGE>

                                      -4-

stock issued after the Original Issue Date pursuant to any stock option and
incentive plan approved by the Board of Directors of the Company, forthwith upon
such issue or sale, the number of shares which may be purchased upon exercise of
this Warrant shall be adjusted (rounded up to the nearest whole share) obtained
by DIVIDING the number of shares which may be acquired upon the exercise of this
Warrant BY a fraction, the NUMERATOR of which shall be the SUM of (i) the number
of shares of Common Stock outstanding immediately prior to such issue or sale
multiplied by the Bid Price PLUS (ii) the consideration received by the Company
upon such issue or sale, and the DENOMINATOR of which shall be the PRODUCT of
(x) the total number of shares of Common Stock outstanding immediately after
such issue or sale, MULTIPLIED by (y) the Bid Price.

         12. FRACTIONAL SHARES. In no event shall any fractional share of Common
Stock be issued upon any exercise of this Warrant. If, upon exercise of this
Warrant as an entirety, the Holder would, except as provided in this Section 12,
be entitled to receive a fractional share of Common Stock, then the Company
shall issue the next higher number of full shares of Common Stock, issuing a
full share with respect to such fractional share.

         13. CERTIFICATE OF ADJUSTMENT. Whenever the Purchase Price is adjusted,
as herein provided, the Company shall promptly deliver to the Holder a
certificate of a firm of independent public accountants setting forth the
Purchase Price after such adjustment and setting forth a brief statement of the
facts requiring such adjustment.

         14. NOTICES OF RECORD DATE, ETC. In the event of:

                  (a) any taking by the Company of a record of the holders of
any class of securities for the purpose of determining the holders thereof who
are entitled to receive any dividend or other distribution, or any right to
subscribe for, purchase or otherwise acquire any shares of stock of any class or
any other securities or property, or to receive any other right,

                  (b) any reclassification of the capital stock of the Company,
capital reorganization of the Company, consolidation or merger involving the
Company, or sale or conveyance of all or substantially all of its assets, or

                  (c) any voluntary or involuntary dissolution, liquidation or
winding-up of the Company,

then and in each such event the Company will mail or cause to be mailed to the
Holder a notice specifying (i) the date on which any such record is to be taken
for the purpose of such dividend, distribution or right, and stating the amount
and character of such dividend, distribution or right, or (ii) the date on which
any such reclassification, reorganization, consolidation, merger, sale or
conveyance, dissolution, liquidation or winding-up is to take place, and the
time, if any is to be fixed, as of which the holders of record in respect of
such event are to be determined. Such notice shall be mailed at least twenty
(20) days prior to the date specified in such notice on which any such action is
to be taken.

<PAGE>

                                      -5-

         15. AMENDMENT. The terms of this Warrant may be amended, modified or
waived only with the written consent of the Company and the Holder hereof.

         16. WARRANT REGISTER; TRANSFERS, ETC.

                  A. The Company will maintain a register containing the names
and addresses of the registered holders of the Warrant. The Holder may change
its address as shown on the warrant register by written notice to the Company
requesting such change. Any notice or written communication required or
permitted to be given to the Holder may be given by certified mail or delivered
to the Holder at its address as shown on the warrant register.

                  B. Subject to compliance with applicable federal and state
securities laws, this Warrant may be transferred by the Holder with respect to
any or all of the shares purchasable hereunder. Upon surrender of this Warrant
to the Company, together with the assignment hereof properly endorsed, for
transfer of this Warrant as an entirety by the Holder, the Company shall issue a
new warrant of the same denomination to the assignee. Upon surrender of this
Warrant to the Company, together with the assignment hereof properly endorsed,
by the Holder for transfer with respect to a portion of the shares of Common
Stock purchasable hereunder, the Company shall issue a new warrant to the
assignee, in such denomination as shall be requested by the Holder hereof, and
shall issue to such Holder a new warrant covering the number of shares in
respect of which this Warrant shall not have been transferred.

                  C. In case this Warrant shall be mutilated, lost, stolen or
destroyed, the Company shall issue a new warrant of like tenor and denomination
and deliver the same (i) in exchange and substitution for and upon surrender and
cancellation of any mutilated Warrant, or (ii) in lieu of any Warrant lost,
stolen or destroyed, upon receipt of evidence reasonably satisfactory to the
Company of the loss, theft or destruction of such Warrant (including a
reasonably detailed affidavit with respect to the circumstances of any loss,
theft or destruction) and of indemnity reasonably satisfactory to the Company.

         17. CERTAIN OBLIGATIONS. This Warrant has been issued subject to
certain obligations to register the Common Stock under the Securities Act of
1933, as amended, which obligations are set forth in the Agreement, of even date
herewith, between the Company, and Paramount, which are incorporated herein by
reference.

         18. NO IMPAIRMENT. The Company will not, by amendment of its
certificate of incorporation, as amended or through any reclassification,
capital reorganization, consolidation, merger, sale or conveyance of assets,
dissolution, liquidation, issue or sale of securities or any other voluntary
action, avoid or seek to avoid the observance or performance of any of the terms
of this Warrant, but will at all times in good faith assist in the carrying out
of all such terms and in the taking of all such action as may be necessary or
appropriate in order to protect the rights of the Holder.

         19. GOVERNING LAW. The provisions and terms of this Warrant shall be
governed by and construed in accordance with the internal laws of the
Commonwealth of Massachusetts.

<PAGE>

                                      -6-

         20. SUCCESSORS AND ASSIGNS. This Warrant shall be binding upon the
Company's successors and assigns and shall inure to the benefit of the Holder's
successors, legal representatives and permitted assigns.

         21. BUSINESS DAYS. If the last or appointed day for the taking of any
action required or the expiration of any right granted herein shall be a
Saturday or Sunday or a legal holiday in the Commonwealth of Massachusetts, then
such action may be taken or right may be exercised on the next succeeding day
which is not a Saturday or Sunday or such a legal holiday.

Dated: March 9, 2000                                REPLIGEN CORPORATION

(Corporate Seal)                                    By:
                                                       -------------------------
                                                      Name: Walter Herlihy
Attest:                                               Title: President and CEO

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

<PAGE>

                                      -7-

                                  Subscription

To:                                              Date:
   ---------------------------                        --------------------------

         The undersigned hereby subscribes for __________ shares of Common Stock
covered by this Warrant. The certificate(s) for such shares shall be issued in
the name of the undersigned or as otherwise indicated below:

                                                 -------------------------------
                                                 Signature

                                                 -------------------------------
                                                 Name for Registration

                                                 -------------------------------
                                                 Mailing Address

                            Net Issue Election Notice

To:                                              Date:
  -----------------------------                       --------------------------

         The undersigned hereby elects under Section 4 to surrender the right to
purchase _______ shares of Common Stock pursuant to this Warrant. The
certificate(s) for the shares issuable upon such net issue election shall be
issued in the name of the undersigned or as otherwise indicated below.

                                                 -------------------------------
                                                 Signature

                                                 -------------------------------
                                                 Name for Registration

                                                 -------------------------------
                                                 Mailing Address

<PAGE>

                                      -8-

                                   Assignment

         For value received ____________________________ hereby sells,

assigns and transfers unto _____________________________________________________

________________________________________________________________________________
    Please print or typewrite name and address of Assignee

________________________________________________________________________________

the within Warrant, and does hereby irrevocably constitute and appoint
_______________________ its attorney to transfer the within Warrant on the books
of the within named Company with full power of substitution on the premises.

Dated:_______________________

                                                ________________________________

In the Presence of:

_____________________________

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