Document:

<PAGE>

                                                                   Exhibit 10.57

                        COOPERATIVE TECHNOLOGY AGREEMENT

                  IN THIS AGREEMENT, Jomed International i Helsingborg AB,
having a principal office at Drottninggatan 94, S-25221, Helsingborg, Sweden,
("Jomed") and Vista Medical Technologies ("Vista"), a Delaware corporation
having a principal office at 5451 Avenida Encinas, Carlsbad, CA 92008, hereby
agree as follows:

                             ARTICLE I - BACKGROUND

         WHEREAS:

         1.1      Vista has products known as Series 8000 Visualization and
Information Systems and certain related products.

         1.2      Vista owns and licenses intellectual property ("IP") rights
and technology related to the design, manufacture and operation of its products.
Vista conducts continuing research and development directed to improvements,
modifications and additions to its products.

         1.3      Jomed sells devices for interventional cardiology and cardiac
surgery and other thoracic surgical applications, and Jomed has considerable
experience in the development marketing, sale and service of such devices and
systems for such applications.

         1.4      Jomed desires an exclusive right of distribution of certain
products made by Vista in certain defined fields and territories corresponding
to Jomed's current and anticipated markets, and Vista is willing to grant to
Jomed such a distribution right pursuant to the terms and conditions of a
certain distribution agreement ("Distribution Agreement") concurrently executed
by the parties.

         1.5      Jomed and Vista recognize that application of Vista's products
in Jomed's fields will require development of improved and modified products,
and Vista and Jomed, therefore, have agreed to conduct co-operative research and
development pursuant to the terms and conditions of this Agreement.

         NOW THEREFORE, in consideration of the representations, warranties,
covenants and agreements contained herein, and for other valuable consideration,
the receipt and adequacy of which is hereby acknowledged, the parties mutually
agree as follows:

                            ARTICLE II - DEFINITIONS

         2.1      "Cooperative Development Area" shall mean research and
development on Vista Improvements, integration of Vista Products and Jomed
Products in the Jomed Field and on integration of the Vista Products and Jomed
Products with other appropriate products or technologies which are capable of
being used in the Jomed Field and the Vista Field.

         2.2      "Effective Date" shall mean May 1, 2000.

<PAGE>

         2.3      "Jomed Core Technology" shall mean all patents, trade secrets
and know-how owned by Jomed or its Related Companies on the date of this
Agreement or subsequently developed or acquired by Jomed or its Related
Companies.

         2.4      "Jomed Field" shall mean all:

                  (a)      Cardiology, including, without limitation,
                           interventional cardiology and related interventional
                           radiological applications.

                  (b)      Cardiothoracic surgery.

         2.5      "Jomed Products" shall mean Jomed's and its Related Companies'
products having application in the Jomed Field.

         2.6      "Series 8000" shall mean the current version of Vista's
visualization and related information systems for interventional cardiology and
cardiothoracic surgery, together with all associated accessories, software and
disposables specific to such systems, together with any updates, modifications
or new versions thereof.

         2.7      "Vista Core Technology" shall mean all patents, trade secrets
and know-how owned by Vista or its Related Companies on the date of this
Agreement or subsequently developed or acquired by Vista or its Related
Companies relating to the Series 8000.

         2.8      "Vista Current Products" shall mean the Series 8000 and
related products, including, without limitation, the apparatus and software
listed in Schedule A of the Distribution Agreement.

         2.9      "Vista Field" shall mean cardiothoracic surgery.

         2.10     "Vista Improvements" shall mean any modified Vista Current
Product and any addition to the Series 8000 product line.

         2.11     "Vista Products" shall mean and include Vista Current Products
and any Vista Improvements that subsequently become subject to the Distribution
Agreement pursuant to its terms.

         2.12     "Work Plan" shall mean a written summary of the tasks to be
undertaken during a particular calendar year or other specified period in
connection with the conduct of activities contemplated by this Agreement,
together with a budget of the anticipated costs associated therewith, adopted by
the parties in accordance with this Agreement. Each Work Plan will include
reasonably detailed descriptions of the tasks and work to be performed, the
scheduling of tasks and work, the resources required to accomplish the work, the
costs associated with the planned work and whether Vista or Jomed will be
responsible for accomplishing each task.

                                       2
<PAGE>

         2.13     "Related Company" shall mean (a) a corporation, firm or
association which, or an individual who, owns a controlling interest in a party
hereto by stock ownership or otherwise, (b) a corporation, firm or association
in which a party hereto owns a controlling interest by stock ownership or
otherwise, or (c) a corporation, firm or association in which a controlling
interest by stock ownership or otherwise is owned by a corporation, firm or
association which, or an individual who, also owns a controlling interest in a
party hereto by stock ownership or otherwise. A "controlling interest" shall
mean ownership or control of more than 50% of the shares of stock entitled to
vote for the election of directors in the case of a corporation, or more than
50% of the voting power in the case of a business entity other than a
corporation.

                      ARTICLE III - VISTA RESPONSIBILITIES

         3.1      Vista shall work exclusively (except of itself) with Jomed in
the Cooperative Development Area.

         3.2      In the calendar year 2000, Vista shall continue to invest in
research and development ("R&D") on its core technology and such improvements as
are appropriate will be incorporated in the Series 8000, according to mutual
agreement with Jomed, taking normal commercial considerations into account.

         3.3      In calendar years after 2000 during the term of this
Agreement, Vista shall continue to invest in core technology, but will
additionally agree with Jomed on specific improvements or enhancements to the
Series 8000, or related products, specifically applicable to the Jomed Field.
Such mutually agreed specific improvements or enhancements, detailed in a Work
Plan, will be funded by payment from Jomed to Vista on a schedule also to be
agreed. Such payments by Jomed will not total more than $850,000 over calendar
years 2001 and 2002.

         3.4      Vista shall develop a preliminary draft of the Work Plan for
2001 by no later than October 31, 2000, and for each subsequent year during the
term of this Agreement by no later than October 31 of the prior calendar year.

         3.5      At its discretion, Vista may disclose Vista Core Technology to
Jomed in furtherance of the purposes of this Agreement.

         3.6      Any Jomed Core Technology disclosed to Vista pursuant to this
Agreement shall be used by Vista solely in the performance of its obligations
under the Work Plan and under the Distribution Agreement.

                       ARTICLE IV - JOMED RESPONSIBILITIES

         4.1      Jomed shall work exclusively (except of itself) with Vista in
the Cooperative Development Area.

         4.2      Jomed shall periodically meet and confer with Vista as deemed
necessary by the parties to coordinate their respective activities in the
Cooperative Development Area. Jomed

                                       3
<PAGE>

shall review each preliminary Work Plan submitted by Vista within thirty (30)
days after receipt of such plan.

         4.3      At its discretion, Jomed may disclose Jomed Core Technology to
Vista in furtherance of the purposes of this Agreement.

         4.4      Any Vista Core Technology disclosed to Jomed pursuant to this
Agreement shall be used by Jomed solely in the performance of its obligations
under the Work Plan and under the Distribution Agreement.

                      ARTICLE V - CONFIDENTIAL INFORMATION

         5.1      "Confidential Information" as used in this Agreement shall
mean all technical or business information disclosed by either party to the
other pursuant to this Agreement that is in tangible form and identified in
tangible form as being confidential and proprietary to the disclosing party or
that is disclosed orally or by demonstration, identified at the time of
disclosure as being confidential and proprietary to the disclosing party, and,
within thirty (30) days after such disclosure, is confirmed in a writing
identified as confidential and proprietary. No information shall be regarded as
Confidential Information if the receiving party can show by competent proof that
such information:

                  (a)      was, at the time of disclosure, already known by the
                           receiving party, as shown by written records in the
                           possession of receiving party;

                  (b)      was at the time of disclosure, or subsequently
                           became, through no fault of the receiving party known
                           to the general public through publication or
                           otherwise; or

                  (c)      was, subsequent to disclosure to the receiving party,
                           lawfully and independently received by the receiving
                           party from a third party who had the right to
                           disclose it without restriction.

Specific aspects or details of Confidential Information shall not be deemed to
be within the public domain or in the possession of receiving party merely
because the Confidential Information is embraced by general disclosures in the
public domain or in the possession of receiving party. In addition, any
combination of Confidential Information shall not be considered in the public
domain or in the possession of receiving party merely because individual
elements thereof are in the public domain or in the possession of receiving
party unless the combination and its principles are in the public domain or in
the possession of receiving party.

         5.2      Either party, at its discretion, may disclose to the receiving
party any Confidential Information that the disclosing party, in its reasonable
judgment, believes is sufficient to enable the receiving party to perform under
this Agreement.

                                       4
<PAGE>

         5.3      Each party agrees:

                  (a)      to treat as confidential and to preserve the
                           confidentiality of all Confidential Information
                           disclosed to it by the other party;

                  (b)      to use any and all Confidential Information disclosed
                           by the other party solely in connection with
                           performance under this Agreement and the Distribution
                           Agreement and for no other purpose;

                  (c)      to make no disclosures of any Confidential
                           Information to any party other than its officers and
                           employees having a reasonable need to know; and

                  (d)      to maintain in confidence any information regarding
                           the nature or scope of any transaction between the
                           parties hereto, except to the extent such information
                           must be disclosed pursuant to law, and then only
                           after notifying the other party of such requirement.

Any obligation imposed by this paragraph 5.3 may be waived in writing by the
disclosing party as to its particular Confidential Information and to a
particular use or disclosure. Any such waiver shall have a one-time effect and
shall not apply to any subsequent situation regardless of its similarity.

         5.4      All Confidential Information shall remain the property of the
disclosing party and, upon request of the disclosing party, the receiving party
shall promptly return to the disclosing party all Confidential Information, or
any part or reproduction thereof.

         5.5      The obligations of the receiving party and each employee and
officer of the receiving party under this Agreement with respect to Confidential
Information shall expire five (5) years from the date of termination of this
Agreement

                             ARTICLE VI - WORK PLAN

         6.1      The parties shall work together in good faith to approve a
Work Plan for 2001 by no later than October 31, 2000. With respect to each
subsequent calendar year during the term of this Agreement, the parties shall
work together in good faith to adopt a Work Plan by no later than October 31 of
the prior calendar year.

                       ARTICLE VII - INTELLECTUAL PROPERTY

         7.1      Each party shall retain ownership of all patents, copyrights,
trademarks, trade secrets, know-how and Confidential Information (collectively
"IP") owned by it on the Effective Date of this Agreement.

         7.2      Any invention or original work made during the performance of
the Work Plan or any other development work performed in the Cooperative
Development Area during the term of this Agreement, regardless of the employment
of the inventors or creators, that is derived solely

                                       5
<PAGE>

from Vista Core Technology shall be owned solely by Vista (hereafter "Vista
Invention"). All IP directed to a Vista Invention shall be owned by Vista. To
the extent any officers, employees, contractors or agents (collectively,
"Employees") of Jomed were involved in making a Vista Invention, Jomed shall
cause such parties to assign their interest in such Vista Invention, and
associated IP, to Vista. Further, Jomed shall have a non exclusive license to
use any invention created by such Employees as prescribed under the legislation
of the European Community.

         7.3      Any invention or original work made during performance of the
Work Plan or any other development work performed in the Cooperative Development
Area during the term of this Agreement, regardless of the employment of the
inventors or creators, that is derived solely from Jomed Core Technology shall
be owned solely by Jomed (hereafter "Jomed Invention"). All IP directed to a
Jomed Invention shall be owned by Jomed. To the extent Vista Employees were
involved in making a Jomed Invention, Vista shall cause such parties to assign
their interest in such Jomed Invention, and associated IP, to Jomed. Further,
Vista shall have a non exclusive license to use any invention created by any
officers, employees, contractors or agents of Vista as prescribed under the
legislation of the European Community.

         7.4      In the event Employees of either Vista and/or Jomed, in
performance of the Work Plan under this Agreement, make an invention or original
work that is not derived solely from Vista Core Technology or Jomed Core
Technology ("Joint Invention"), such Joint Invention shall be owned jointly by
Vista and Jomed. Each party agrees to make full disclosure to the other party of
any such Joint Invention and any background information related thereto. The
parties agree to cooperate with each other in obtaining and maintaining IP
direct to such Joint Invention.

         7.5      Each party agrees to execute and deliver all documents
reasonably necessary to carry out the intentions of this Article VII.

                          ARTICLE VIII - FORCE MAJEURE

         8.1      "Force Majeure" shall mean any event or condition, not
existing as of the date of signature of this Agreement, not reasonably
foreseeable as of such date and not reasonably within the control of either
party, which prevents, in whole or in material part, the performance by one of
the parties of its obligations hereunder, such as act of God, act of government,
war or related actions, civil insurrection, riot, sabotage, strike or other
labor disturbance, epidemic, fire, flood, windstorm, and similar event.

         8.2      Upon giving notice to the other party, a party affected by an
event of Force Majeure shall be released without any liability on its part from
the performance of its obligations under this Agreement, except for the
obligation to pay any amounts due and owing hereunder, but only to the extent
and only for the period that its performance of such obligations is prevented by
the event of Force Majeure.

         8.3      During the period that the performance by one of the parties
of its obligations under this Agreement has been suspended by reason of an event
of Force Majeure, the other party may likewise suspend the performance of all or
part of its obligations hereunder to the extent that such suspension is
commercially reasonable.

                                       6
<PAGE>

                        ARTICLE IX - TERM AND TERMINATION

         9.1      This Agreement shall commence on the Effective Date and may be
terminated by either party upon providing at least thirty (30) days written
notice to the other upon the earlier of (i) the expiration or termination of the
Distribution Agreement or (ii) upon the termination of Jomed's rights to
distribute Vista Products on an exclusive basis in the fields identified in the
Distribution Agreement.

         9.2      The provisions of paragraph 5.5 and Article VII hereof shall
survive the expiration or termination of this Agreement.

                            ARTICLE X - MISCELLANEOUS

         10.1     This Agreement does not make either party the employee, agent
or legal representative of the other for any purpose whatsoever. Neither party
is granted any right or authority to assume or to create any obligation or
responsibility, express or implied, on behalf of or in the name of the other
party. In fulfilling its obligations pursuant to this Agreement, each party
shall be acting as an independent contractor.

         10.2     This Agreement shall be binding upon and inure to the benefit
of the parties hereto and the successors or permitted assigns of the parties
hereto. The Agreement is personal to the parties and cannot be assigned by
either party without the prior written consent of the other party, provided,
however, that Jomed may assign this Agreement and all rights and obligations to
a Related Company of Jomed or to any person who succeeds to substantially all of
the assets and business of Jomed to which this Agreement relates.

         10.3     This Agreement and the Exclusive Distribution Agreement
constitute the entire agreement between the parties hereto with respect to the
subject matter hereof and supersede all prior agreements whether written or oral
relating thereto.

         10.4     This Agreement shall be governed by and interpreted in
accordance with the laws of the State of California, including all matters of
construction, validity, performance and enforcement, without giving effect to
principles of conflict of laws.

         10.5     All of the representations, warranties, and covenants made in
this Agreement, and all terms and provisions hereof intended to be observed and
performed by the parties after the termination hereof, shall survive such
termination and continue thereafter in full force and effect.

         10.6     The failure of any party hereto to enforce at any time any of
the provisions of this Agreement shall in no way be construed to be a waiver of
any such provision, nor in any way to affect the validity of this Agreement or
any part thereof or the right of the party thereafter to enforce each and every
such provision. No waiver of any breach of this Agreement shall be held to be a
waiver of any other or subsequent breach. Any amendment to this Agreement shall
be in writing and signed by the parties hereto.

                                       7
<PAGE>

         10.7     This Agreement may be executed in any number of counterparts,
each of which shall be deemed as original and all of which together shall
constitute one instrument.

         10.8     The titles and headings to Sections herein are inserted for
the convenience of reference only and are not intended to be a part of or to
affect the meaning or interpretation of this Agreement. This Agreement shall be
construed without regard to any presumption or other rule requiring construction
hereof against the party causing this Agreement to be drafted.

         10.9     Nothing in this Agreement, expressed or implied, is intended
to confer on any person other than the parties to this Agreement or their
respective successors or assigns, any rights, remedies, obligations or
liabilities under or by reason of this Agreement. Except as specifically
granted, nothing in this Agreement shall be construed as a grant by one party to
the other of a license under any IP rights of the one party.

         10.10    All notices or other communications to a party required or
permitted hereunder shall be deemed given if in writing and delivered personally
or sent by telecopy (with confirmation of transmission) or certified mail
(return receipt requested) to such party at the following addresses (or at such
other addresses as shall be specified by like notice):

         if to Jomed to:

                  Jomed International i Helsingborg AB
                  Drottninggatan 94
                  S-25221 Helsingborg
                  Sweden
                  Attention:  Antti Ristinmaa
                              Chief Financial Officer
                              Fax (46) 42 490 6001

         and if to Vista to:

                  Vista Medical Technologies, Inc.
                  5451 Avenida Encinas, Suite A
                  Carlsbad, CA  92008
                  Attention:  John Lyon
                  FAX (760) 603-9170

         with a copy to:

                  Brobeck Phleger & Harrison LLP
                  12390 El Camino Real
                  San Diego, CA  92130
                  Attention:  Michael Kagnoff
                  FAX (858) 720-2555

                                       8
<PAGE>

Jomed or Vista may change their respective above-specified recipient and/or
mailing address by notice to the other party given in the manner herein
prescribed. All notices shall be deemed given on the day when actually delivered
as provided above (if delivered personally or by telecopy) or on the day shown
on the return receipt (if delivered by mail) or on the next day following
delivery to a reputable overnight carrier.

         10.11    In the event any provision of this Agreement shall be declared
invalid, illegal or unenforceable, the validity, legality and enforceability of
the remaining provisions shall not in any way be affected or impaired thereby.

         10.12    Each of the parties to this Agreement hereby agrees with the
other parties hereto that, except as may be required to comply with the
requirements of applicable law or any exchange upon which such party's capital
stock is listed or traded, no press release or similar public announcement or
communication will be made or caused to be made concerning the execution or
performance of this Agreement unless specifically approved in advance by Jomed
and Vista. The foregoing shall not restrict either party's communications with
employees, customers or private investors.

         10.13    Each party agrees to execute and deliver without further
consideration any further applications, licenses, assignments or other
documents, and to perform such other lawful acts as the other party may
reasonably require to fully secure and/or evidence the rights or interests
herein.

                [Remainder of This Page Intentionally Left Blank]

                                       9
<PAGE>

         IN WITNESS WHEREOF, each of the parties has caused this Sales Agreement
to be executed in the manner appropriate to each, as of the date first above
written.

                                       VISTA MEDICAL TECHNOLOGIES, INC.

                                       By: /s/ Robert DeVaere
                                          -----------------------------
                                       Title: V.P. Finance, CFO
                                             --------------------------
                                       Date:  May 19, 2000
                                             --------------------------

                                       JOMED

                                       By:
                                          -----------------------------
                                       Title:
                                             --------------------------
                                       Date:
                                             --------------------------

                                       10
<PAGE>

                                   SCHEDULE A
                         CURRENT PRODUCT CONFIGURATIONS

        VISTA SERIES 8000, ADVANCED VISUALIZATION AND INFORMATION SYSTEM

STANDARD EQUIPMENT

SERIES 8000 NTSC   SERIES 8005 PAL
(110V)                        (220V)
<TABLE>
<CAPTION>

---------------------------- ------------------------- ------------------------------------------------------------- -------
PART #                       PART #                    DESCRIPTION                                                   QTY
---------------------------- ------------------------- ------------------------------------------------------------- -------
<S>                          <C>                       <C>                                                           <C>
8075-1                       8076                      CardioConsole (Inc Shelf for lightsource)                     1
---------------------------- ------------------------- ------------------------------------------------------------- -------
5131.011                     5131.001                  Wolf Lightsource, 300 Watt Xenon                              1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8170-1                       8170P-1                   3D/2D CardioController II                                     1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8180                         8180P                     CardioView Processor                                          1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8176                         8176                      Head Mounted Display (HMD) with Ext. cable                    2
---------------------------- ------------------------- ------------------------------------------------------------- -------
8271                                                   Sony 13" Analog Monitor                                       1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8190                         8190P                     StereoScope Camera                                            1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8191-01                      8191-01                   Stereo Endoscope 10mm, 0 degree                               1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8191-02                      8191-02                   Stereo Endoscope 10mm, 30 degree                              1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8054-1                                                 Liquid Light Guide                                            1
---------------------------- ------------------------- ------------------------------------------------------------- -------

SPECIAL ORDER MINI-CAMERA PACKAGE

---------------------------- ------------------------- ------------------------------------------------------------- -------
8100                         8100P                     CardioCamera 3D - 50mm                                        1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8050                         8050                      CardioLight (rack mounted)                                    1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8060                         8060                      Lamp Housing Module                                           1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8054                         8054                      CardioCamera Light Guide (single fiber)                       1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8110-02                      8110-02                   Thoracic 3D holder (malleable)                                1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8120-01                      8120-01                   Gooseneck 3D Arm                                              1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8120-02                      8120-02                   Gooseneck 3D Holder for Gooseneck Arm                         1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8150-03                      8150-03                   Universal Clamp                                               1
---------------------------- ------------------------- ------------------------------------------------------------- -------

SPECIAL ORDER MONO, ENDOCAM PACKAGE

---------------------------- ------------------------- ------------------------------------------------------------- -------
8160                         8160P                     2D Endoscope Camera Head                                      1
---------------------------- ------------------------- ------------------------------------------------------------- -------
8032-1                       8032-1                    32mm Endoscope Coupler                                        1
---------------------------- ------------------------- ------------------------------------------------------------- -------

</TABLE>

                                       11<PAGE>

                                                                     EXHIBIT 4.3

                          ENERGY BIOSYSTEMS CORPORATION

                                       And

                              SOCIETY NATIONAL BANK

                                  Rights Agent

                          STOCKHOLDER RIGHTS AGREEMENT

                            Dated as of March 8,1995

<PAGE>

                                Table of Contents

<TABLE>

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

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

Section 3.      Issue of Rights Certificates..........................    5

Section 4.      Form of Rights Certificates...........................    7

Section 5.      Countersignature and Registration.....................    8

Section 6.      Transfer, Split Up, Combination and
                Exchange of Rights Certificates; Mutilated,
                Destroyed, Lost or Stolen Rights
                Certificates..........................................    8

Section 7.      Exercise of Rights; Purchase Price;
                Expiration Date of Rights.............................    9

Section 8.      Cancellation and Destruction of Rights Certificates...    11

Section 9.      Reservation and Availability of Capital Stock.........    11

Section 10.     Preferred Shares Record Date..........................    12

Section 11.     Adjustment of Purchase Price, Number of Shares or
                Number of Rights......................................    12

Section 12.     Certificate of Adjusted Purchase Price or Number
                of Shares.............................................    19

Section 13.     Consolidation, Merger or Sale or Transfer of Assets
                or Earning Power......................................    20

Section 14.     Fractional Rights and Fractional Shares...............    21

Section 15.     Rights of Action......................................    22

Section 16.     Agreement of Right Holders............................    22

Section 17.     Rights Certificate Holder Not Deemed a Stockholder....    23

Section 18.     Concerning the Rights Agent...........................    23

Section 19.     Merger or Consolidation or Change of Name of
                Rights Agent..........................................    24

Section 20.     Duties of Rights Agent................................    24

Section 21.     Change of Rights Agent................................    26

Section 22.     Issuance of New Rights Certificates...................    27

Section 23.     Redemption............................................    27

Section 24.     Notice of Certain Events..............................    28
</TABLE>

<PAGE>

<TABLE>

<S>             <C>                                                     <C>
Section 25.     Notices.............................................    29

Section 26.     Supplements and Amendments..........................    30

Section 27.     Successors..........................................    31

Section 28.     Benefits of this Agreement..........................    31

Section 29.     Severability........................................    31

Section 30.     Governing Law.......................................    31

Section 31.     Counterparts........................................    31

Section 32.     Descriptive Heading.................................    31

Signatures      ....................................................    32
</TABLE>

Exhibit A -  Form of Certificate of Designation of Series One Junior
             Participating Preferred Stock of Energy BioSystems Corporation

Exhibit B -  Form of Rights Certificate

Exhibit C -  Summary of Rights to Purchase Preferred Stock

<PAGE>

                          STOCKHOLDER RIGHTS AGREEMENT

         This Agreement, dated as of March 8, 1995, between Energy BioSystems
Corporation, a Delaware corporation (the "Company"), and Society National
Bank, a national banking corporation, as Rights Agent (the "Rights Agent").

                                    RECITALS

         WHEREAS, on March 8, 1995 (the "Rights Dividend Declaration Date"),
the Board of Directors of the Company authorized and declared a dividend of
one preferred share purchase right (a "Right") for each Common Share (as
defined herein) of the Company outstanding at the close of business on March
27, 1995 (the "Record Date"), each Right representing the right to purchase
one one-hundredth of a share of Series One Junior Participating Preferred
Stock, par value $0.01 per share, of the Company, having the rights, powers
and preferences set forth in the form of Certificate of Designation attached
hereto as Exhibit A, upon the terms and subject to the conditions set forth
herein, and authorized and directed the issuance of one Right with respect to
each Common Share that shall become outstanding between the Record Date and
the earlier of the Distribution Date, the Redemption Date and the Final
Expiration Date (as defined herein).

         Accordingly, 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:

         (a) " ACQUIRING PERSON " shall mean any Person (as such term is
hereinafter defined) who or which, together with all Affiliates and
Associates (as such terms are hereinafter defined) of such Person, shall be
the Beneficial Owner (as such term is hereinafter defined) of 20% or more of
the Common Shares of the Company then outstanding, but shall not include (i)
the Company, (ii) any Subsidiary (as such term is hereinafter defined) of the
Company, (iii) any employee benefit plan of the Company or of any Subsidiary
of the Company or any Person or entity holding shares of capital stock of the
Company for or pursuant to the terms of any such plan, in its capacity as an
agent or trustee for any such plan, (iv) Ethyl Corporation, a Delaware
corporation ("Ethyl"), (v) Gryphon Ventures II, Limited Partnership, a
Massachusetts limited partnership ("Gryphon") and (vi) William M. Haney, III
("Haney"). Notwithstanding the foregoing, 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 20% or
more of the Common Shares of the Company then outstanding; provided, however,
that if a Person shall become the Beneficial Owner of 20% or more of the
Common Shares of the Company then outstanding by reason of share purchases by
the Company and shall, after such share purchases by the Company, become the
Beneficial Owner of any additional Common Shares of the Company, then such
Person shall be deemed to be an "Acquiring Person."

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

<PAGE>

         (c) 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, except as provided in
Section l(c)(ii)(A)hereof;

         (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), or upon the exercise of conversion rights,
exchange rights, rights (other than the Rights), warrants, options or
otherwise; provided, however, that a Person shall not be deemed the
Beneficial Owner of, or to beneficially own, securities tendered pursuant to
a tender or exchange offer made by or on behalf of such Person or any of such
Person's Affiliates or Associates until such tendered securities are accepted
for payment, 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 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 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) for the purpose of
acquiring, holding, voting (except to the extent contemplated by the proviso
to Section l(c)(ii)(B)) or disposing of any securities of the Company.

         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.

         {d) "Board Approval" means the adoption or approval by the Company's
Board of Directors {including the affirmative vote or approval of a majority
of Continuing Directors) at a meeting duly called and held at which a quorum
was present and acting throughout, provided that at the time of such adoption
or approval there are not less than three Continuing Directors.

         (e) "Business Day" shall mean any day other than a Saturday, Sunday,
or a day on which banking institutions in the State of Texas are authorized
or obligated by law or executive order to close.

         (f) "Close of Business" on any given date shall mean 5:00 p.m.,
Houston, Texas time, on such date; provided, however, that if such date is
not a Business Day it shall mean 5:00 p.m., Houston, Texas time, on the next
succeeding Business Day.

<PAGE>

         (g) "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
and, to the extent that at the time Rights are exercised there are not a
sufficient number of Company Common Shares authorized to permit the full
exercise of the Rights, shares of any other class or series of the Company
designated for such purpose containing terms substantially similar to the
terms of the Company Common Shares. "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
Person is a Subsidiary of another Person, the Person or Persons which
ultimately control such first-mentioned Person.

         (h) "Continuing Director" shall mean (i) any member of the Board of
Directors of the Company, while such Person is a member of the Board, who is
not an Acquiring Person, or an Affiliate or Associate of an Acquiring Person,
or a representative of any Acquiring Person or of any such Affiliate or
Associate, and who was a member of the Board prior to the date of this
Agreement, or (ii) any Person who subsequently becomes a member of the Board,
while such Person is a member of the Board, who is not an Acquiring Person,
or an Affiliate or Associate of an Acquiring Person, or a representative of
an Acquiring Person or of any such Affiliate or Associate, if such Person's
nomination for election or election to the Board is recommended or approved
by a majority of the Continuing Directors.

         (i) "Exchange Act" shall mean the Securities Exchange Act of 1934,
as amended, as in effect on the date of this Agreement.

         (j) "Person" shall mean any individual, partnership, firm, corporation
or other entity, and shall include any successor (by merger or otherwise) of
such entity, as well as any syndicate or group deemed to be a person under
Section 14(d)(2) of the Exchange Act.

         (k) "Preferred Share" shall mean a share of Series One Junior
Participating Preferred Stock, par value $0.01 per share of the Company and, to
the extent that at the time the rights are exercised there are not a sufficient
number of shares of Series One Junior Participating Preferred Stock authorized
to permit the full exercise of the Rights, shares of any other series of
Preferred Stock of the Company designated for such purpose containing terms
substantially similar to the terms of the Series One Junior Participating
Preferred Stock.

         (l) "Preferred Share Fraction" shall mean one one-hundredth of a
Preferred Share.

         (m)"Record Date" shall have the meaning set forth in the preamble
hereto.

         (n)"Right" shall have the meaning set forth in the preamble hereto.

         (o) "Rights Dividend Declaration Date" shall have the meaning set forth
in the preamble hereto.

         (p) "Section 13 Event" shall mean any event described in clauses (i),
(ii) or (iii) of Section 13(a) hereof.

         (q) "Shares Acquisition Date" shall mean the first date of public
announcement (which for purposes of this definition shall include, without

<PAGE>

limitation, a report filed pursuant to Section 13(d) under the Exchange Act)
by the Company or an Acquiring Person that an Acquiring Person has become
such.

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

         (s) The following terms are defined herein in the Sections set forth
below:

<TABLE>
<CAPTION>
                    Term                   Section
                    ----                   -------
        <S>                                <C>
          "Adjustment Shares".........           11
          "common stock equivalents"..           11
          "current market prlce"......           11
          "Current Value".............           11
          "Distribution Date".........            3
          "equivalent preferred
            shares"...................           11
          "Ethyl".....................         1(a)
          "Final Expiration Date".....            7
          "Gryphon" ..................         1(a)
          "Haney" ....................         1(a)
          "Purchase Price"............            4
          "Redemption Date"...........            7
          "Redemption Price"..........           23
          "Rights Certificate"........            3
          "Section 11(a)(ii) Trigger
            Date".....................           11
          "Security"..................           11
          "Spread"....................           11
          "Substitution Period".......           11
          "Summary of Rights".........            3
          "Trading Day"...............           11
</TABLE>

         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. Contemporaneously with such appointment, if any, the Company shall
notify the Rights Agent thereof. In the event the Company appoints one or more
Co-Rights Agents, the respective duties of the Rights Agent and any Co-Rights
Agents shall be as the Company shall determine.

Section 3. ISSUE OF RIGHTS CERTIFICATES.

(a) Until the earlier of (i) the close of business on the 30th day after the
Shares Acquisition Date and (ii) the close of business on the 3Oth day after the
date that a tender or exchange offer 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 shares of capital stock of the
Company for or pursuant to the terms of any such plan, in its capacity as an
agent or trustee for any such plan, Ethyl, Gryphon or Haney) is first published
or sent or given within the meaning of Rule 14d-2(a) (or any successor rule) of
the General Rules and Regulations under the Exchange Act, the consummation of
which would result in any Person becoming the Beneficial Owner of Common Shares
aggregating 20% or more of the then outstanding Common Shares (including any

<PAGE>

such date which is after the date of this Agreement and prior to the issuance of
the Rights; the earlier of such dates being herein referred to as the
Distribution Date"), (x) the Rights will be evidenced (subject to the provisions
of paragraph (b) of this Section 3) by the certificates for Common Shares
registered in the names of the holders thereof (which certificates for Common
Shares shall also be deemed to be certificates for the Rights) and not by
separate certificates, and (y) the Rights and interests therein will be
transferable only in connection with the transfer of the associated 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, one or more Rights
certificates, in substantially the form of Exhibit B hereto (a "Rights
Certificate"), evidencing one Right for each Common Share so held, subject to
adjustment as provided herein. In the event that an adjustment in the number of
Rights per Common Share has been made pursuant to Section 11(n) hereof, then at
the time of distribution of the Rights Certificates, the Company shall make the
necessary and appropriate rounding adjustments (in accordance with Section 14(a)
hereof) so that Rights Certificates representing only whole numbers of Rights
are distributed and cash is paid in lieu of any fractional Rights. As of and
after the Distribution Date, the Rights will be evidenced solely by such Rights
Certificates.

         (b) As promptly as practicable following the Record Date, the Company
will send or cause to be sent a copy of a Summary of Rights to Purchase
Preferred Stock, in substantially the form attached hereto as EXHIBIT C (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 close of business on the
Record Date, until the Distribution Date, the Rights will be evidenced by such
certificates for Common Shares registered in the names of the holders thereof
(together with a copy of the Summary of Rights). Until the earliest of the
Distribution Date, the Redemption Date and the Final Expiration Date, the
transfer of any certificate for Common Shares outstanding at the close of
business 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 represented thereby.

         (c) Rights shall, without any further action, be issued in respect of
all Common Shares that are issued (including any Common Shares held in treasury)
after the Record Date but prior to the earlier of the Distribution Date, the
Redemption Date and the Final Expiration Date. Certificates issued for Common
Shares (including, without limitation, certificates issued upon transfer or
exchange of Common Shares, certificates evidencing an original issuance and
certificates for reacquired Common Shares referred to in the last sentence of
this subsection (c)) after the Record Date but prior to the earliest of the
Distribution Date, the Redemption Date or 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 Stockholder Rights
                  Agreement between Energy BioSystems Corporation (the
                  "Company") and Society National Bank dated as of

<PAGE>

                  March 8, 1995 (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 the Company. 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. The Company will mail to
                  the holder of this certificate a copy of the Rights
                  Agreement, as in effect on the date of mailing, without
                  charge after receipt of a written request therefore.
                  Under certain circumstances described in the Rights
                  Agreement, Rights issued to, or held by, any person who
                  is, was or becomes an Acquiring Person or any Affiliate
                  or Associate thereof (as defined in the Rights
                  Agreement), whether currently held by or on behalf of
                  such Person or by any subsequent holder, may become null
                  and void.

With respect to such certificates containing the foregoing legend, until the
earlier of (i) the Distribution Date and (ii) the Final Expiration Date, the
Rights associated with the Common Shares represented by such certificates shall
be evidenced by such certificates alone and registered holders of Common Shares
shall also be the registered holders of the associated Rights, and the 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 Distribution Date, any Rights associated with such Common Shares shall be
deemed cancelled and retired so that the Company shall not be entitled to
exercise any Rights associated with the Common Shares which are no longer
outstanding.

Section 4. FORM OF RIGHTS CERTIFICATES.

         (a) The Rights Certificates (and the form of election to purchase
shares and certification of status and form of assignment and certification of
status 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 on which the Rights may from time to time be listed, or to conform to
usage. The Rights Certificates shall be in machine printable form and in a
format reasonably satisfactory to the Rights Agent. Subject to the provisions of
Section 22 hereof, the Rights Certificates, whenever issued, shall be dated as
of the Record Date and shall show the date of countersignature by the Rights
Agent, and on their face shall entitle the holders thereof to purchase such
number of Preferred Share Fractions as shall be set forth therein at the price
set forth therein (such exercise price per Preferred Share Fraction being
hereinafter referred to as the "Purchase Price"), but the number of such
Preferred Share Fractions and the Purchase Price shall be subject to adjustment
as provided herein.

         (b) Any Rights Certificate issued pursuant to Section 3(a) or Section
22 hereof that represents Rights that the Company knows are beneficially owned
by: (i) an Acquiring Person or any Associate or Affiliate of an Acquiring
Person, (ii) a transferee of an Acquiring Person (or of any such Associate or
Affiliate)

<PAGE>

who becomes a transferee after the Acquiring Person becomes such, or (iii) a
transferee of an Acquiring Person (or of any such Associate or Affiliate) who
becomes a transferee prior to or concurrently with the Acquiring Person
becoming such and receives such Rights pursuant to either (A) a transfer
(whether or not for consideration) from the Acquiring Person to holders of
equity interests in such Acquiring Person or to any Person with whom such
Acquiring Person has any continuing oral or written plan, agreement,
arrangement or understanding regarding the transferred Rights or (B) a
transfer that the Board of Directors of the Company has determined is part of
an oral or written plan, agreement, arrangement or understanding that has as
a primary purpose or effect avoidance of Section 7(e) hereof, and any Rights
Certificate issued pursuant to Section 6 or Section 11 hereof upon transfer,
exchange, replacement or adjustment of any other Rights Certificate referred
to in this sentence, shall contain (to the extent feasible) the following
legend:

The Rights represented by this Rights Certificate are or were beneficially owned
by a Person who was or became an Acquiring Person or an Mfiliate or Associate of
an Acquiring Person (as such terms are defined in the Rights Agreement) .
Accordingly, this Rights Certificate and the Rights represented hereby may
become null and void in the circumstances specified in Section 7(e) of the
Rights Agreement.

Section 5. Countersignature and Registration.

         (a) The Rights Certificates shall be executed on behalf of the Company
by its Chairman of the Board of Directors, President or any Vice President and
attested by its Secretary or an Assistant Secretary, either manually or by
facsimile signature, and shall have affixed thereto the Company's seal or a
facsimile thereof. The Rights Certificates shall be manually or by facsimile
signature countersigned by an authorized signatory of the Rights Agent, but it
shall not be necessary for the same signatory to countersign all of the Rights
Certificates hereunder. No Rights Certificate shall be valid for any purpose
unless so countersigned. In case any officer of the Company who shall have
signed any of the Rights Certificates shall cease to be such officer of the
Company before countersignature by the Rights Agent and issuance and delivery by
the Company, such Rights 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 Rights Certificates had not ceased
to be such officer of the Company; and any Rights Certificate may be signed on
behalf of the Company by any person who, at the actual date of the execution of
such Rights Certificate, shall be a proper officer of the Company to sign such
Rights 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 in Cleveland, Ohio, books for
registration and transfer of the Rights Certificates issued hereunder. Such
books shall show the names and addresses of the respective holders of the Rights
Certificates, the number of Rights evidenced on its face by each of the Rights
Certificates and the date and certificate number of each of the Rights
Certificates.

         Section 6. TRANSFER, SPLIT UP, COMBINATION AND EXCHANGE OF RIGHTS
CERTIFICATES; MUTILATED, DESTROYED, LOST OR STOLEN RIGHTS CERTIFICATES.

         (a) Subject to the provisions of Section 4(b), Section 7(e) and Section
14 hereof, at any time after the close of business on the Distribution Date, and
at or prior to the close of business on the earlier of the Redemption Date or
the

<PAGE>

Final Expiration Date, any Rights Certificate or Rights Certificates may be
transferred, split up, combined or exchanged for another Rights Certificate
or Rights Certificates, entitling the registered holder to purchase a like
number of Preferred Share Fractions as the Rights Certificate or Rights
Certificates surrendered then entitled such holder to purchase. Any
registered holder desiring to transfer, split up, combine or exchange any
Rights Certificate shall make such request in writing delivered to the Rights
Agent, and shall surrender the Rights Certificate or Rights 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 Rights Certificate or Rights Certificates, as
the case may be, as so requested. The Company may require payment from the
holders of Rights Certificates ofa sum sufficient to cover any tax or
governmental charge that may be imposed in connection with any transfer,
split up, combination or exchange of such Rights 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 Rights
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 Rights Certificate if mutilated, the Company will make and deliver a new
Rights Certificate of like tenor to the Rights Agent for delivery to the
registered owner in lieu of the Rights Certificate so lost, stolen, destroyed or
mutilated.

Section 7. EXERCISE OF RIGHTS; PURCHASE PRICE; EXPIRATION DATE OF RIGHTS.

         (a) The registered holder of any Rights Certificate may exercise the
Rights evidenced thereby (except as otherwise provided herein) in whole or in
part at any time after the Distribution Date upon surrender of the Rights
Certificate, with the form of election to purchase and certification of status
on the reverse side thereof duly executed, to the Rights Agent at the office of
the Rights Agent designated for such purpose together with payment of the
Purchase Price for each Preferred Share Fraction as to which the Rights are
exercised, at or prior to the earliest of (i) the close of business on March 8,
2005 (the "Final Expiration Date") or (ii) the time at which the Rights are
redeemed as provided in Section 23 hereof (the "Redemption Date").

         (b) The Purchase Price for each Preferred Share Fraction issuable
pursuant to the exercise of a Right shall initially be $50.00, 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 Rights Certificate representing exercisable
Rights, with the form of election to purchase and certification of status duly
executed, accompanied by payment of the Purchase Price for such Preferred Share
Fraction or Preferred Share Fractions (or other shares, securities or property,
as the case may be) to be purchased and an amount equal to any applicable
transfer tax required to be paid by the holder of such Rights Certificate in
accordance with Section 9 hereof by certified or cashier's check or money order
payable to the order of the Company, the Rights Agent shall, subject to Section
20(k) hereof, thereupon (i)(A) promptly requisition from any transfer agent of
the Preferred Shares (or make available, if the Rights Agent is the transfer
agent) certificates for the number of Preferred Share Fractions to be purchased
and the

<PAGE>

Company hereby irrevocably authorizes its transfer agent to comply with all
such requests, or (B) if the Company shall have elected to deposit the total
number of Preferred Share Fractions issuable upon exercise of the Rights
hereunder with a depositary agent, requisition from the depositary agent
depositary receipts representing such number of Preferred Share Fractions as
are to be purchased (in which case certificates for the Preferred Share
Fractions represented by such receipts shall be deposited by the transfer
agent with the depositary agent) and the Company hereby directs the
depositary 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 shares in accordance with Section 14 hereof, (iii)
promptly after receipt of such certificates or depositary receipts, cause the
same to be delivered to or upon the order of the registered holder of such
Rights Certificate, registered in such name or names as may be designated by
such holder and, (iv) when appropriate, after receipt, promptly deliver such
cash to or upon the order of the registered holder of such Rights
Certificate. In the event that the Company is obligated to issue other
securities (including Common Shares} of the Company, pay cash and/or
distribute other property pursuant to Section 11 (a) hereof, the Company will
make all arrangements necessary so that such other securities, cash and/or
property are available for distribution by the Rights Agent, if and when
appropriate.

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

         (e) Notwithstanding anything in this Agreement to the contrary, from
and after the date that a Person shall become an Acquiring Person, any Rights
beneficially owned by (i) an Acquiring Person or an Associate or Affiliate of an
Acquiring Person, (ii) a transferee of an Acquiring Person (or of any such
Associate or Affiliate) who becomes a transferee after the Acquiring Person
becomes such, or (iii) a transferee of an Acquiring Person (or of any such
Associate or Affiliate) who becomes a transferee prior to or concurrently with
the Acquiring Person becoming such and receives such Rights pursuant to either
(A) a transfer (whether or not for consideration) from the Acquiring Person to
holders of equity interests in such Acquiring Person or to any Person with whom
the Acquiring Person has any continuing oral or written plan, agreement,
arrangement or understanding regarding the transferred Rights or (B) a transfer
which the Board of Directors of the Company has determined is part of an oral or
written plan, agreement, arrangement or understanding which has as a primary
purpose or effect the avoidance of this Section 7(e), shall become null and void
without any further action and no holder of such Rights shall have any rights
whatsoever with respect to such Rights, whether under any provision of this
Agreement or otherwise. The Company shall use all reasonable efforts to ensure
that the provisions of this Section 7(e) and Section 4(b) hereof are complied
with, but shall have no liability to any holder of Rights Certificates or other
Person as a result of its failure to make any determinations with respect to an
Acquiring Person or its Affiliates, Associates or transferees hereunder.

         (f) 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 the certification of status contained
following the appropriate form of election to purchase set forth on the reverse

<PAGE>

side of the Rights Certificate surrendered for such exercise shall have been
completed and signed by the registered holder thereof and the Company shall have
been provided with 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 RIGHTS CERTIFICATES. All
Rights 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 cancelled form,
or, if surrendered to the Rights Agent, shall be cancelled by it, and no Rights
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 Rights Certificate acquired by the Company
otherwise than upon the exercise thereof. The Rights Agent shall deliver all
cancelled Rights Certificates to the Company, or shall, at the written request
of the Company, destroy such cancelled Rights Certificates, and in such case
shall deliver a certificate of destruction thereof to the Company.

         Section 9. RESERVATION AND AVAILABILITY OF CAPITAL STOCK.

         (a) The Company covenants and agrees that it will cause to be reserved
and kept available out of its authorized and unissued Preferred Shares, or any
authorized and issued Preferred Shares held in its treasury (and, following the
occurrence of a Distribution Date, out of its authorized and unissued Common
Shares and/or other securities or out of its authorized and issued shares held
in its treasury) the number of Preferred Shares (and, following the occurrence
of a Distribution Date, Common Shares and/or other securities) that will be
sufficient to permit the exercise in full of all outstanding Rights.

         (b) If hereafter the Preferred Shares issuable upon the exercise of
Rights are listed on any national securities exchange or included in the Nasdaq
Stock Market, the Company shall use its best efforts to cause, from and after
such time as the Rights become exercisable (but only to the extent that it is
reasonably likely that the Rights will be exercised), all shares reserved for
such issuance to be so listed on such exchange or included in the Nasdaq Stock
Market upon official notice of issuance upon such exercise, as the case may be.

         (c) The Company covenants and agrees that it will take all such action
as may be necessary to ensure that all Preferred Share Fractions (and, following
the occurrence of a Distribution Date, Common Shares and/or other securities)
delivered upon exercise of Rights shall, at the time of delivery of the
certificates for such shares (subject to payment of the Purchase Price), be duly
and validly authorized and issued and fully-paid and nonassessable shares.

         (d) The Company further covenants and agrees that it will pay, when due
and payable, any and all Federal and state original issue and transfer taxes and
charges which may be payable in respect of the issuance or delivery of the
Rights Certificates or of any Preferred Shares (or Common Shares and/or other
securities, as the case may be) 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 Rights Certificates to a person other
than, or the issuance or delivery of certificates or depositary receipts for the
Preferred Shares (or Common Shares and/or other securities, as the case may be)
in a name other than that of, the registered holder of the Rights Certificate
evidencing Rights surrendered for exercise or to issue or deliver any

<PAGE>

certificates or depositary receipts for Preferred Shares or Common 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 Rights Certificate at the time of surrender)
or until it has been established to the Company's satisfaction that no such tax
is due.

         Section 10. PREFERRED SHARES RECORD DATE. Each person in whose name any
certificate for a number of Preferred Share Fractions (or Common Shares and/or
other securities, as the case may be) is issued upon the exercise of Rights
shall for all purposes be deemed to have become the holder of record of the
Preferred Share Fractions (or Common Shares and/or other securities, as the case
may be) represented thereby on, and such certificate shall be dated, the date
upon which the Rights Certificate evidencing such Rights was duly surrendered
and payment of the Purchase Price (and any applicable transfer taxes) was made;
provided, however, that if the date of such surrender and payment is a date upon
which the Preferred Shares (or Common Shares and/or other securities, as the
case may be) transfer books of the Company are closed, such person shall be
deemed to have become the record holder of such shares (fractional or otherwise)
on, and such certificate shall be dated, the next succeeding Business Day on
which the Preferred Shares (or Common Shares and/or other securities, as the
case may be) transfer books of the Company are open. Prior to the exercise of
the Rights evidenced thereby, the holder of a Rights Certificate, as such, shall
not be entitled to any rights of a stockholder of the Company with respect to
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 kind and number of shares or other securities
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 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), except
as otherwise provided in this Section 11(a) and Section 7(e) hereof, 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 Preferred Shares or other shares of capital stock, as the
case may be, issuable on such date, shall be proportionately adjusted so that
the holder of any Right exercised after such time shall be entitled to receive,
upon payment of the adjusted Purchase Price, the aggregate number and kind of
Preferred Shares or other shares of capital stock, as the case may be, which, if
such Right had been exercised immediately prior to such date and at a time when
the Preferred Shares transfer books of the Company were open, 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

<PAGE>

shall be made prior to, any adjustment required pursuant to Section 11(a)(ii)
hereof.

         (ii) In the event that any Person (other than (i) the Company, (ii) any
Subsidiary of the Company, (iii) any employee benefit plan of the Company or of
any Subsidiary of the Company or any Person or entity holding shares of capital
stock of the Company for or pursuant to the terms of any such plan, in its
capacity as an agent or trustee for any such plan, (iv) Ethyl, (v) Gryphon or
(vi) Haney), alone or together with its Affiliates and Associates, shall, at any
time after the Rights Dividend Declaration Date, become an Acquiring Person
then, promptly following the first occurrence of such event, proper provision
shall be made so that each holder of a Right (except as provided in Section 7(e)
hereof) shall thereafter have the right to receive, upon exercise thereof at the
then current Purchase Price in accordance with the terms of this Agreement and
in lieu of Preferred Share Fractions, such number of Common Shares of the
Company as shall equal the result obtained by (x) multiplying the then current
Purchase Price by the then number of Preferred Share Fractions for which a Right
is then exercisable and (y) dividing that product (which shall thereafter be
referred to as the "Purchase Price" for each Right and for all purposes of this
Agreement) by 50% of the then current market price (determined pursuant to
Section 11(d) hereof) per Common Share on the fifth day after the date on which
a Person has become an Acquiring Person, or the fifth day after the Shares
Acquisition Date, whichever market price shall be less (such number of shares
being hereinafter referred to as the " Adjustment Shares"). 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.

         (iii) In the event that the number of Common Shares which are
authorized by the Company's Certificate of Incorporation but not outstanding or
reserved for issuance for purposes other than upon exercise of the Rights are
not sufficient to permit the exercise in full of the Rights in accordance with
the foregoing subparagraph (ii) of this Section 11(a), the Company shall: (A)
determine the excess of (1) the value of the Adjustment Shares issuable upon the
exercise of a Right (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 the Adjustment Shares, upon payment of the
applicable Purchase Price, (1) cash, (2) a reduction in the Purchase Price, (3)
other equity securities of the Company (including, without limitation, shares,
or units of shares, of preferred stock which the Company's Board of Directors in
office at the time has determined upon Board Approval have the same value as the
Common Shares (such shares or units of shares of preferred stock, the "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 Board Approval
of the Company's Board of Directors in office at the time based upon the advice
of a nationally recognized investment banking firm selected by the Board of
Directors of the Company; provided, however, that if the Company shall not have
made adequate provision to deliver value pursuant to clause (B) above within 30
days following the later of (x) the first occurrence of the date on which a
Person has become an Acquiring Person or the Shares Acquisition Date and (y) the
date on which the Company's right of redemption pursuant to Section 23(a)
expires (the later of (x) and (y) being referred to herein as 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, Common Shares (to the extent available) and then, if necessary,
cash, which shares and/or cash have an aggregate value equal to the Spread. If

<PAGE>

the Company's Board of Directors shall determine by Board Approval that it is
likely that sufficient additional Common Shares could be authorized for issuance
upon exercise in full of the Rights, the 30-day period set forth above may be
extended to the extent necessary, but not more than 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 Section 7(e)
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 issue a public announcement stating that the
exercisability of the Rights has been temporarily suspended as well as a public
announcement at such time as the suspension is no longer in effect. For purposes
of this Section 11(a)(iii), the value of the Common Shares shall be the current
market price (as determined pursuant to Section 11(d) hereof) per share 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 case 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 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 current per share
market price of the Preferred Shares (as determined pursuant to Section 11(d>>
on such record date, 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
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 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, and shall be binding on the Company, the Rights
Agent and the holders of the Rights. 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 adjustments shall be made successively whenever such a
record date is fixed; and in the event that such rights, options or warrants are

<PAGE>

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 periodic cash dividend at a rate not in excess
of 125% of the rate of the last regular periodic cash dividend theretofore paid
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 current market price of one Preferred Share
Fraction {as determined pursuant to Section 11{d) hereof) 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 Fraction and the denominator of which shall be
such current market price of one Preferred Share Fraction; 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. 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 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
market price" per share 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 market price per share of the
Security is determined during any 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 the requisite 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
market price" shall be appropriately adjusted to take into account ex-dividend
trading. The closing price for each Trading 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 Security
is 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
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, as
reported by the Nasdaq Stock Market 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

<PAGE>

in the Security selected by the Board of Directors of the Company. If on any
such date no market maker is making a market in the Security, the fair value
of such shares on such date as determined in good faith by the Board of
Directors of the Company shall be used. 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 market
price" per Preferred Share shall be determined in accordance with the method set
forth above for the Securities in clause (i) of this Section 11(d). If the
current market price per Preferred Share cannot be determined in the manner
provided above or if the Preferred Shares are not publicly held or listed or
traded in a manner described in clause (i) of this Section 11(d), the "current
market price" per Preferred Share shall be conclusively deemed to be an amount
equal to the current market price per share of the Common Shares (appropriately
adjusted for such events as stock splits, stock dividends and recapitalizations
with respect to the Common Shares occurring after the date of this Agreement),
multiplied by 100. If neither the Common Shares nor the Preferred Shares are
publicly held or so listed or traded, "current market price" per share 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. For all purposes of this Agreement, the "current
market price" of a Preferred Share Fraction shall be equal to the "current
market price" of one Preferred Share divided by 100.

         (e) No adjustment in the Purchase Price shall be required unless such
adjustment would require an increase or decrease of at least 1% in such price;
provided, 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 ten-thousandth of a share in the case of
Common Shares or other shares or one-millionth of a share in the case of
Preferred Shares, 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 the earlier of (i) three years from the date of the transaction which
requires such adjustment or (ii) the Final Expiration Date.

         (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,
thereafter the number of such other shares so receivable upon exercise of any
Right shall 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 this Section 11 and the provisions of Sections
7,9,10,13 and 14 hereof 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 Preferred Share
Fractions 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) hereof, upon each adjustment of the Purchase Price as a result of

<PAGE>

the calculations made in Sections 11(b) and (c) hereof, 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 Preferred
Share Fractions (calculated to the nearest one-millionth of a Preferred Share)
obtained by (i) multiplying (x) the number of Preferred Share Fractions 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 Preferred Share Fractions issuable upon the exercise
of a Right. Each of the Rights outstanding after such adjustment of the number
of Rights shall be exercised for the number of Preferred Share Fractions 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 ten-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 Rights Certificates have been issued, shall be at least
ten days later than the date of the public announcement. If Rights Certificates
have been issued, 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 Rights Certificates on such record date
Rights 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 Rights Certificates held by
such holders prior to the date of adjustment, and upon surrender thereof, if
required by the Company, new Rights Certificates evidencing all the Rights to
which such holders shall be entitled after such adjustment. Rights Certificates
to be so distributed shall be issued, executed and countersigned in the manner
provided for herein {and may bear, at the option of the Company, the adjusted
Purchase Price) and shall be registered in the names of the holders of record of
Rights 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 Preferred Share Fractions issuable upon the exercise of the
Rights, the Rights Certificates theretofore and thereafter issued may continue
to express the Purchase Price and the number of Preferred Share Fractions which
were expressed in the initial Rights Certificates issued hereunder.

         (k) Before taking any action that would cause an adjustment reducing
the Purchase Price below one one-hundredth of the then par value, if any, of the
Preferred Shares issuable upon exercise of the Rights or below the then par
value, if any, of the Common Shares if then 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 nonassessable Preferred Shares or, if applicable, Common
Shares at such adjusted Purchase Price.

<PAGE>

         (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 (fractional or otherwise) 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 consolidation or subdivision of the Preferred Shares, issuance
wholly for cash of any of the Preferred Shares at less than the current market
price, issuance wholly for cash of Preferred Shares or securities which by their
terms are convertible into or exchangeable for Preferred Shares, stock dividends
or issuance of rights, options or warrants referred to hereinabove in this
Section 11, hereafter made by the Company to holders of its Preferred Shares
shall not be taxable to such stockholders.

         (n) Anything in this Agreement to the contrary notwithstanding, in the
event that the Company shall at any time prior to the Distribution Date (i)
declare or pay any dividend on the outstanding Common Shares payable in Common
Shares or (ii) effect a subdivision, combination or consolidation of the Common
Shares (by reclassification or otherwise than by payment of dividends in Common
Shares) into a greater or lesser number of Common Shares, then in any such case
(A) the number of Preferred Share Fractions purchasable after such event upon
proper exercise of each Right shall be determined by multiplying the number of
Preferred Share Fractions so purchasable immediately prior to such event by a
fraction, the numerator of which shall be the total number of Common Shares
outstanding immediately prior to the occurrence of the event and the denominator
of which shall be the total number of Common Shares outstanding immediately
following the occurrence of such event, (B) the Purchase Price to be in effect
after such event shall be determined by multiplying the Purchase Price in effect
immediately prior to such event by a fraction, the numerator of which shall be
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 (C) 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. If an event occurs which would require
an adjustment under Section 11(a)(ii) and this Section 11(n), the adjustment
provided for in this Section 11(n) shall be in addition to and prior to any
adjustment required pursuant to Section 11(a)(ii).

         Section 12. CERTIFICATE OF ADJUSTED PURCHASE PRICE OR NUMBER OF SHARES.
Whenever an adjustment is made as provided in Sections 11 and 13 hereof, the
Company shall (a) promptly prepare a certificate signed by officers authorized
to execute a Rights Certificate in Section 5 setting forth such adjustment, and
a brief statement of the facts accounting for such adjustment, (b) promptly file

<PAGE>

with the Rights Agent and with each transfer agent for the Preferred Shares and
the Common Shares a copy of such certificate and (c) mail a brief summary
thereof to each holder of a Rights Certificate in accordance with Section 25
hereof. The Rights Agent shall be fully protected in relying on any such
certificate and on any adjustment therein contained and shall not be deemed to
have knowledge of any such adjustment unless and until it shall have received
such certificate.

         Section 13. (a) CONSOLIDATION. MERGER OR SALE OR TRANSFER OF ASSETS OR
EARNING POWER. In the event that, following the Shares Acquisition Date,
directly or indirectly, (i) the Company shall consolidate with, or merge with
and into, any other Person and the Company shall not be the continuing or
surviving corporation of such consolidation or merger, (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 consolidation
or merger and, in connection with such consolidation or 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 more than 50% of the assets or earning power
of the Company and its Subsidiaries (taken as a whole) to any Person or Persons
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 Preferred Share
Fractions for which a Right is then exercisable, in accordance with the terms of
this Agreement and in lieu of Preferred Share Fractions, such number of Common
Shares of such other Person (including the Company as successor thereto or as
the surviving corporation) free and clear of all liens, encumbrances, rights of
first refusal or other adverse claims, as shall be equal to the result obtained
by (1) multiplying the then-current Purchase Price by the number of Preferred
Share Fractions for which a Right is then exercisable and (2) dividing that
product by 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 Section 13 Event, 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, it being specifically intended that the provisions of Section 11 hereof
shall apply only to such issuer following the first occurrence of a Section 13
Event; 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 its Common Shares thereafter deliverable upon
the exercise of the Rights.

         (b) 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,

<PAGE>

warrants, instruments or securities outstanding or any agreements or
arrangements which, as a result of the consummation of such transaction,
would substantially diminish or otherwise eliminate the benefits intended to
be afforded by the Rights. The Company 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 provisions of this Section 13 shall
similarly apply to successive mergers or consolidations or sales or other
transfers.

         Section 14. FRACTIONAL RIGHTS AND FRACTIONAL SHARES.

         (a) The Company shall not be required to issue fractions of Rights or
to distribute Rights Certificates which evidence fractional Rights. In lieu of
such fractional Rights, there shall be paid to the registered holders of the
Rights 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 as reported by the Nasdaq Stock Market or such other system then in use
or, if on any such date the Rights are 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, whose determination shall
be described in a statement filed with the Rights Agent.

         (b) The Company shall not be required to issue fractions of shares
(other than fractions which are integral multiples of one one-hundredth of a
Preferred Share) upon exercise of the Rights or to distribute certificates which
evidence fractional shares (other than fractions which are integral multiples of
one one-hundredth of a Preferred Share). Fractions of Preferred Shares in
integral multiples of one one-hundredth of a Preferred Share may, at the
election of the Company, be evidenced by depositary receipts, pursuant to an
appropriate agreement between the Company and a depositary selected by it,
provided that such agreement shall provide that the holders of such depositary
receipts shall have all the rights, privileges and preferences to which they are
entitled as beneficial owners of the Preferred Shares represented by such
depositary receipts. In lieu of fractional shares that are not integral
multiples of one one-hundredth of a Preferred Share, the Company may pay to the
registered holders of Rights 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 or one Common Share as the case may be. For
purposes of this Section 14(b), the current market value of a Common Share or a
Preferred Share shall be the current market price of a Common Share (as

<PAGE>

determined pursuant to Section 1 l(d)(i) hereof) or a Preferred Share (as
determined pursuant to Section 11(d)(ii) hereof), as the case may be, 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 his right to receive any fractional Rights or any fractional shares
(other than fractions which are integral multiples of one one-hundredth of a
Preferred Share} upon exercise of a Right (except as provided above}.

         Section 15. RIGHTS OF ACTION. All rights of action in respect of this
Agreement, except the rights of action given to the Rights Agent under Section
18 hereof, are vested in the respective registered holders of the Rights
Certificates (and, prior to the Distribution Date, the registered holders of the
Common Shares); and any registered holder of any Rights Certificate (or, prior
to the Distribution Date, of the Common Shares), without the consent of the
Rights Agent or of the holder of any other Rights Certificate (or, prior to the
Distribution Date, of the Common Shares), may, in his own behalf and for his own
benefit, enforce this Agreement, and may institute and maintain any suit, action
or proceeding against the Company to enforce this Agreement, or otherwise
enforce or act in respect of his right to exercise the Rights evidenced by such
Rights Certificate in the manner provided in such Rights Certificate and in this
Agreement. Without limiting the foregoing or any remedies available to the
holders of Rights, it is specifically acknowledged that the holders of Rights
would not have an adequate remedy at law for any breach of this Agreement and
will be entitled to specific performance of the obligations under, and
injunctive relief against actual or threatened violations of the obligations of
any Person (including, without limitation, the Company) subject to, this
Agreement.

         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 Rights Certificates are
transferable only on the registry books of the Rights Agent if surrendered at
the principal office of the Rights Agent, duly endorsed or accompanied by a
proper instrument of transfer and with the appropriate forms and certificates
fully executed;

         (c) subject to Section 6(a) and Section 7(f) hereof, the Company and
the Rights Agent may deem and treat the Person in whose name the Rights
Certificate (or prior to the Distribution Date, the associated Common Share
certificate) is registered as the absolute owner thereof and of the Rights
evidenced thereby (notwithstanding any notations of ownership or writing on the
Rights Certificates or the associated Common Share certificate made by anyone
other than the Company or the Rights Agent) for all purposes whatsoever, and
neither the Company nor the Rights Agent, subject to the last sentence of
Section 7(e) hereof, shall be affected by any notice to the contrary; and

         (d) notwithstanding anything in this Agreement to the contrary, neither
the Company nor the Rights Agent shall have any liability to any holder of a
Right or a beneficial interest in a Right or other Person as a result of its
inability to perform any of its obligations under this Agreement by reason of
any preliminary or permanent injunction or other order, decree or ruling issued
by a court of competent jurisdiction or by a governmental, regulatory or

<PAGE>

administrative agency or commission, or any statute, rule, regulation or
executive order promulgated or enacted by any governmental authority prohibiting
or otherwise restraining performance of such obligation; provided, however, the
Company must use its best efforts to have any such order, decree or ruling
lifted or otherwise overturned as promptly as practicable.

         Section 17. RIGHTS CERTIFICATE HOLDER NOT DEEMED A STOCKHOLDER. No
holder, as such, of any Rights Certificate shall be entitled to vote, receive
dividends or be deemed for any purpose the holder of the Preferred Shares, the
Common Shares or any other securities of the Company which may at any time be
issuable upon the exercise of the Rights represented thereby, nor shall anything
contained herein or in any Rights Certificate be construed to confer upon the
holder of any Rights 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 24 hereof), or to
receive dividends or subscription rights, or otherwise, until the Right or
Rights evidenced by such Rights 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 in accordance with a fee
schedule to be mutually agreed upon 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 of liability in the
premises.

         (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 Rights
Certificate or certificate for the Preferred Shares or Common Shares or for
other securities of the Company, instrument of assignment or transfer, power of
attorney, endorsement, affidavit, letter, notice, instruction, 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, or otherwise upon the advice of
counsel as set forth in Section 20 hereof.

         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 or stock transfer 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

<PAGE>

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

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

         Section 20. DUTIES OF RIGHTS AGENT. The Rights Agent undertakes the
duties and obligations imposed by this Agreement upon the following terms and
conditions, by all of which the Company and the holders of Rights Certificates,
by their acceptance thereof, shall be bound:

         (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.

         (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 anyone of the Chairman of the Board of
Directors, the President or any Vice President 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 Rights
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 Rights 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 Rights Certificate; nor shall it

<PAGE>

be responsible for any change in the exercisability of the Rights (including the
Rights becoming void pursuant to Section 7(e) hereof) or 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 change or adjustment (except with respect to
the exercise of Rights evidenced by Rights Certificates after actual notice that
such change or adjustment is required); nor shall it by any act hereunder be
deemed to make any representation or warranty as to the authorization or
reservation of any Preferred Shares or Common Shares to be issued pursuant to
this Agreement or any Rights Certificate or as to whether any Preferred Shares
or Common 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 anyone
of the Chairman of the Board of Directors, the President or any Vice President
of the Company, and to apply to such officers for advice or instructions in
connection with its duties under this Rights Agreement, 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.

         (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 pecuniarily 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.

         (j) At any time and from time to time after the Distribution Date, upon
the request of the Company, the Rights Agent shall promptly deliver to the
Company a list, as of the most recent practicable date (or as of such earlier
date as may be specified by the Company), of the holders of record of Rights.

         (k) If, with respect to any Rights Certificate surrendered to the
Rights Agent for exercise or transfer, the certificate of status attached to the
form of assignment or form of election to purchase, as the case may be, has
either not been completed or indicates an affirmative response to clause l or 2
thereof, the Rights Agent shall not take any further action with respect to the
requested exercise or transfer without first consulting with the Company.

         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

<PAGE>

upon 30 days' notice in writing mailed to the Company and to each transfer agent
of the Preferred Shares or Common Shares by registered or certified mail, and to
the holders of the Rights 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 Preferred Shares or Common Shares by
registered or certified mail, and to the holders of the Rights Certificates by
first-class mail. If the Rights Agent shall resign or be removed or shall
otherwise become incapable of acting, the resigning, removed, or incapacitated
Rights Agent shall remit to the Company, or to any successor Rights Agent
designated by the Company, all books, records, funds, certificates or other
documents or instruments of any kind then in its possession which were acquired
by such resigning, removed or incapacitated Rights Agent in connection with its
services as Rights Agent hereunder, and shall thereafter be discharged from all
duties and obligations hereunder. Following notice of such removal, resignation
or incapacity, the Company shall appoint a successor to such 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 Rights Certificate (who shall, with such notice, submit his
Rights Certificate for inspection by the Company), then the registered holder of
any Rights 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 either (a) a corporation organized
and doing business under the laws of the United States or of the State of New
York or Texas (or of any other state of the United States so long as such
corporation is authorized to do business as a banking institution in the State
of New York or Texas), in good standing, having an office or an affiliate with
an office in the State of New York which is authorized under such laws to
exercise corporate trust or stock transfer 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 $50
million or (b) an affiliate of a corporation described in clause (a) of this
sentence which is a corporation organized and doing business under the laws of
the United States or of the State of New York or Texas (or of any other state of
the United States so long as such corporation is authorized to do business as a
banking institution in the State of New York or Texas), in good standing, having
a principal office in the State of New York, which is authorized under such laws
to exercise corporate trust or stock transfer powers and is subject to
supervision or examination by federal or state authority. 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 or Preferred Shares, and mail a
notice thereof in writing to the registered holders of the Rights 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.

         Section 22. ISSUANCE OF NEW RIGHTS CERTIFICATES. Notwithstanding any of
the provisions of this Agreement or of the Rights to the contrary, the Company
may, at its option, issue new Rights Certificates evidencing Rights in such form

<PAGE>

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 Rights Certificates made in
accordance with the provisions of this Agreement.

         Section 23. REDEMPTION.

         (a) The Board of Directors of the Company may, at its option, at any
time prior to 5:00 p.m., Houston time on the earlier of(i) the 30th day after
the Shares Acquisition Date and (ii) the Final Expiration Date, redeem all but
not less than all the then outstanding Rights at a redemption price of $0.01 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") and the Company may, at its
option, pay the Redemption Price either in Common Shares (based on the current
per share market price thereof (as determined pursuant to Section 11(d) hereof)
or cash; provided, however, that if the Board of Directors of the Company
authorizes redemption of the Rights in either of the circumstances set forth in
clauses (i) and (ii) below, then such authorization to redeem must be by Board
Approval: (i) such authorization occurs on or after the time a Person becomes an
Acquiring Person, or (ii) such authorization occurs on or after the date of a
change (resulting from a proxy or consent solicitation) in a majority of the
directors in office at the commencement of such solicitation if any Person who
is a participant in such solicitation has stated (or, if upon the commencement
of such solicitation, the Company's Board of Directors has in good faith
determined upon Board Approval) that such Person (or any of its Affiliates or
Associates) intends to take, or may consider taking, any action which would
result in such Person becoming an Acquiring Person or which would cause the
occurrence of a Section 13 Event. Notwithstanding anything contained in this
Agreement to the contrary, the Rights shall not be exercisable following the
time that a Person becomes an Acquiring Person until such time as the Company's
right of redemption hereunder has expired.

         (b) Immediately upon the action of the Board of Directors of the
Company ordering the redemption of the Rights, and without any further action
and without any notice, the right to exercise the Rights will terminate and the
only right thereafter of the holders of Rights shall be to receive the
Redemption Price. Within ten days after the action of the Board of Directors
ordering the redemption of the Rights, the Company shall give notice of such
redemption to the holders of the then outstanding Rights by mailing such notice
to all such holders at their last addresses as they appear upon the registry
books of the Rights 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. Each such notice of redemption will 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, and other than in connection with the purchase of Common Shares
prior to the Distribution Date.

         Section 24. NOTICE OF CERTAIN EVENTS.

         (a) In case the Company shall 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
periodic cash dividend at a rate not in excess of 125% of the rate of the last

<PAGE>

regular periodic cash dividend theretofore paid), or (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, or (iii) to effect any reclassification of
its Preferred Shares (other than a reclassification involving only the
subdivision of outstanding Preferred Shares), or (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 more than 50% of the assets or
earning power of the Company and its Subsidiaries (taken as a whole) to any
other Person, or (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 the Rights
Agent and to each holder of a Rights Certificate, in accordance with Section 25
hereof, a notice of such proposed action, which shall specify the record date
for the purposes of such stock dividend, 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 ten 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 ten
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 the event set forth in Section 11(a)(ii) hereof shall
occur, then the Company shall as soon as practicable thereafter give to the
Rights Agent and to each holder of a Rights Certificate, in accordance with
Section 25 hereof, a notice of the occurrence of such event, which shall
describe such event and the consequences of same to holders of Rights under
Section 11(a)(ii) hereof.

         Section 25. NOTICES. Notices or demands authorized by this Agreement to
be given or made by the Rights Agent or by the holder of any Rights 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:

         Energy BioSystems Corporation
         4200 Research Forest Drive
         The Woodlands, Texas 77381
         Attention: President

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
Rights 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:

         Society National Bank
         c/o KeyCorp Shareholder Services
         700 Louisiana, Suite 2620
         Houston, Texas 77002

<PAGE>

         Attention: Lorraine Rodewald

Notices or demands authorized by this Agreement to be given or made by the
Company or the Rights Agent to the holder of any Rights 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.

         Section 26. SUPPLEMENTS AND AMENDMENTS. Prior to the Distribution Date
and subject to the penultimate sentence of this Section 26, the Company and the
Rights Agent shall, if the Company so directs, supplement or amend any provision
of this Agreement without the approval of any holders of Rights. From and after
the Distribution Date and subject to the penultimate sentence of this Section
26, the Company and the Rights Agent shall, if the Company so directs,
supplement or amend this Agreement without the approval of any holders of Rights
in order (i) to cure any ambiguity, (ii) to correct or supplement any provision
contained herein which may be defective or inconsistent with any other
provisions herein, (iii) to shorten or lengthen any time period hereunder, or
(iv) to change or supplement the provisions hereunder in any manner which the
Company may deem necessary or desirable and which shall not adversely affect the
interests of the holders of Rights (other than an Acquiring Person or an
Affiliate or Associate of an Acquiring Person); provided, however, this
Agreement may not be supplemented or amended to lengthen, pursuant to clause
(iii) of this sentence, (A) subject to Section 29 hereof, a time period relating
to when the Rights may be redeemed at such time as the Rights are not then
redeemable, or (B) any other time period unless such lengthening is, based upon
a determination by the Company's Board of Directors upon Board Approval, for the
purpose of protecting, enhancing or clarifying the rights of, and/or the
benefits to, the holders of Rights. Upon the delivery of a certificate from an
appropriate officer of the Company or, so long as any Person is an Acquiring
Person hereunder, from the majority of the Continuing Directors which states
that the proposed supplement or amendment is in compliance with the terms of
this Section 26, the Rights Agent shall execute such supplement or amendment.
Notwithstanding anything contained in this Agreement to the contrary, no
supplement or amendment shall be made which changes the Redemption Price, the
Purchase Price, the Final Expiration Date or the number of Preferred Share
Fractions for which a Right is exercisable without Board Approval. Prior to the
Distribution Date, the interests of the holders of Rights shall be deemed
coincident with the interests of the holders of Common Shares.

         Section 27. 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 28. BENEFITS OF THIS AGREEMENT. Nothing in this Agreement shall
be construed to give to any person or corporation other than the Company, the
Rights Agent and the registered holders of the Rights 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 Rights Certificates (and, prior to the Distribution Date, the
Common Shares).

         Section 29. 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

<PAGE>

force and effect and shall in no way be affected, impaired or invalidated;
provided, however, that notwithstanding anything in this Agreement to the
contrary, if any such term, provision, covenant or restriction is held by such
court or authority to be invalid, void or unenforceable and a majority of the
Continuing Directors determines in its good faith judgment that severing the
invalid language from this Agreement would adversely affect the purpose or
effect of this Agreement and the Rights shall not then be redeemable, the right
of redemption set forth in Section 23 hereof shall be reinstated and shall not
expire until the Close of Business on the tenth Business Day following the date
of such determination by a majority of the Continuing Directors.

         Section 30. GOVERNING LAW. This Agreement and each Rights 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 31. 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 32. DESCRIPTIVE HEADING. 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.

<PAGE>

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

                                             ENERGY BIOSYSTEMS CORPORATION
Attest:

By:      /s/ PAUL G. BROWN III                          /s/ JOHN H. WEBB
     ---------------------------------------         -------------------------
         Paul G. Brown, III                          John H. Webb
         Secretary                                   Chairman, President and
                                                     Chief Executive Officer

                                                     SOCIETY NATIONAL BANK

Attest:

By:      /s/ BARBARA HUBBARD                     By:    /s/ LORRAINE RODEWALD
    ----------------------------------------         --------------------------
Name:    BARBARA HUBBARD                             Lorraine Rodewald
         -----------------------------------         Assistant Vice President
Title:   TRUST OFFICER

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