Document:

<PAGE>   1
*Confidential treatment has been requested with respect to the portions of the
 agreement, indicated with an asterisk [*]. A complete copy of this agreement,
 including the redacted terms, has been separately filed with the Securities and
 Exchange Commission.

                                                                    Exhibit 10.4

                   ELECTRONIC SOFTWARE DISTRIBUTION AGREEMENT

This Agreement is made and entered into on September 1, 1997 by and between
CyberSource Corporation, a California corporation, located at 550 South
Winchester Blvd., Suite 301, San Jose, CA 95128 ("Electronic Reseller") and
McAfee Software, Inc., a Delaware corporation, located at 2805 Bowers Avenue,
Santa Clara, California 95051 ("Vendor").

BACKGROUND

a)   Vendor is the Developer and Owner of all rights (or has a license to sell)
     to the Software identified in Exhibit A.

b)   Vendor desires to enter into a Distribution Agreement with Electronic
     Reseller whereby Electronic Reseller will be responsible for
     electronically packaging Vendor's Software and associated Documentation,
     and electronically distributing such packaged Software Products to
     End-User customers or resellers in accordance with the terms and
     conditions of this Agreement.

c)   Electronic Reseller desires to obtain the right to electronically package
     Vendor's Software and Documentation, and electronically distribute same in
     accordance with the terms of this Agreement.

NOW THEREFORE, the parties hereby agree as follows:

1.   DEFINITIONS

     a)   Software: the executable object code for Vendor's software identified
          on Exhibit A, including all subsequent versions thereof provided to
          Electronic Reseller pursuant to this Agreement.

     b)   Documentation: all computer readable collateral materials normally
          provided from time to time by Vendor to End Users for use of the
          Software, that are identified in Exhibit A, and all subsequent
          versions thereof provided to Electronic Reseller pursuant to this
          Agreement.

     c)   End-User License Agreement: the computer readable license agreement
          attached hereto as Exhibit 8, as modified from time to time, that
          governs the use of the Software by End Users, and which is to be
          included with each copy of the Software sold by the Electronic
          Reseller hereunder.

     d)   Electronic Reseller Materials: computer readable materials provided
          by Electronic Reseller for inclusion in an electronic package
          containing the Software, Documentation, and End-User License
          Agreement, which materials have been approved in advance, in writing,
          by Vendor.

     e)   Product: a copy of the Software, Documentation, End-User License
          Agreement and Electronic Reseller Materials, if any, packaged in
          computer readable form together for electronic delivery on
          software.net(TM) in accordance with this Agreement.

     f)   End User: person(s) or entity(ies) that acquires a Product for use
          rather than resale or distribution.

     g)   Vendor Trademarks: the trademarks, trade names, and logos used by
          Vendor and identified on Exhibit A.

     h)   Territory: all countries in the world only via the Internet except
          (i) countries to which export or re-export of any Product, or the
          direct products of any Product is prohibited by United States law
          without first obtaining the permission of the United states Office of
          Export Administration or its successor, and (ii) countries that may
          be hereafter excluded pursuant to the terms of this Agreement.

2.   LICENSE.

     A.   Rights Granted to Electronic Reseller. Vendor grants Electronic
          Reseller a non-transferable, and non-exclusive license and right to:

          1.   reproduce the Software, Documentation, and the End-User License
               Agreement in computer readable form;

          2.   modify the Documentation to incorporate Electronic Reseller's
               name, subject to prior approval of Vendor;

          3.   package the Software, Documentation, Electronic Reseller
               Materials and the End-User License Agreement in a computer
               readable manner specified by Vendor.

          4.   utilize the Vendor Trademarks in connection with the replication
               of the Software, packaging and distribution of the Products, in
               a manner specified by Vendor; and

          5.   Distribute the Products to End Users or resellers in the
               Territory, subject to the restrictions set forth in this
               Agreement.

     b.   Rights Reserved to Vendor. Electronic Reseller acknowledges that the
          Software and Documentation are the property of Vendor or its
          licensers and that Electronic Reseller has no rights in the foregoing
          except those expressly granted by this Agreement. Nothing herein
          shall be construed as restricting Vendor's right to sell, lease,
          license, modify, publish or otherwise distribute the Software or
          Documentation, in whole or in part, to any other person.
<PAGE>   2
3.   REPRODUCTION BY ELECTRONIC RESELLER.

     a)   Reproduction and Packaging. Electronic Reseller agrees to accurately
          replicate the Software Documentation provided by the Vendor in
          computer readable form, and to package these items as specified by the
          Vendor.

     b)   Vendor Trademarks and Legends. Electronic Reseller shall include
          copies of the Vendor Trademark copyright notices and other proprietary
          rights legends, on all copies of the Documentation and Software that
          it packages in computer readable form, in the manner specified by the
          Vendor.

4.   DISTRIBUTION BY ELECTRONIC RESELLER.

     a)   Inventory. Electronic Reseller will maintain access to
          software.net(TM) sufficient to serve adequately the needs of End User
          Customers.

     b)   Packaging. Electronic Reseller will distribute the Products only via
          the Internet and only as packaged in accordance with this Agreement,
          with all packaging, warranties, disclaimers and End-User License
          Agreements intact. Electronic Reseller will make copies of the
          current End-User License Agreement available to End User customers in
          computer readable form.

     c)   Product Returns. Electronic Reseller agrees to honor any refund
          requests received from End User customers pursuant to the terms of the
          End-User License Agreement relating to Products distributed by
          Electronic Reseller.

     d)   Cost of Distribution. Costs relating to evaluation, packaging and
          distribution of the Software and Documentation shall be borne by the
          Electronic Reseller.

5.   ELECTRONIC RESELLER MARKETING OBLIGATIONS.

     a)   Marketing Efforts. Electronic Reseller agrees to use its best efforts
          to market, promote, sub-license (to End Users only), and distribute
          the most current version of the Software. Such marketing, promotion,
          sublicensing and distribution shall be performed in accordance with
          all applicable laws.

     b)   Reverse Engineering. Electronic Reseller agrees not to: (i)
          disassemble, de-compile or otherwise reverse engineer the Software or
          otherwise attempt to learn the source code, structure, algorithms or
          ideas underlying the Software; (ii) take any action contrary to
          Vendor's End-User License Agreement except as expressly and
          unambiguously allowed under this Agreement.

     c)   End User License Fees. Electronic Reseller shall have the sole
          discretion to set the license fee charge to End Users for the
          Software.

     d)   Customer Registration. Electronic Reseller agrees to provide Vendor
          with customer information, for the purpose of Vendor to register the
          customer into Vendor database for technical support and other related
          issues, including name, address, email address and product purchased.

6.   VENDOR'S DELIVERY OBLIGATIONS.

     a)   Initial Deliverables. Vendor shall deliver the current version of the
          Software Documentation to Electronic Reseller immediately following
          execution of this Agreement. Vendor will provide Electronic Reseller
          with (i) copies of the Software on CD-ROM or master diskettes, (ii)
          Product specification information in HTML format, or in another
          mutually agreeable computer readable form that can be reproduced by
          the Electronic Reseller, (iii) Product Documentation is a computer
          readable form mutually agreeable to the parties that can be reproduced
          by the Electronic Reseller, and (iv) vendor press releases and
          announcements in a computer readable from mutually agreeable to the
          parties that can be reproduced by the Electronic Reseller.

     b)   Deleted.

     c)   New Versions. Vendor shall provide Electronic Reseller with computer
          readable copies of all new releases, updates, or revisions of the
          Software and Documentation within a reasonable time after each such
          release is made generally available by Vendor. Vendor will notify
          Electronic Reseller of its plans for each new release, update or
          revision of the Software or Documentation within a reasonable period
          of time prior to such release.

     d)   New Products. Electronic Reseller understands and acknowledges that
          Vendor continues to review software products available on the market
          and to conduct its own research and development activities with
          respect to the internal development of such new products. Vendor
          makes no representations or warranties with respect to continued
          availability of any of the Software covered by this Agreement, or the
          nature or availability of any future modifications, updates, or
          enhancements thereto. Similarly, Vendor makes no representations
          with respect to any new product offerings it may make in the future,
          the compatibility of such products with the Software covered by this
          Agreement, or the availability of such new products to the Electronic
          Reseller.

<PAGE>   3
7.    VENDOR'S SUPPORT OBLIGATIONS.

      a)    Support for End Users. Vendor will provide support to End Users of
            the Software to be distributed hereunder in accordance with its
            then-current published software policy if any.

      b)    Support for Electronic Reseller. Vendor will provide Electronic
            Reseller, without charge, such technical information, current
            maintenance documentation, and telephone assistance as is necessary
            to enable Electronic Reseller to effectively reproduce, package and
            distribute the Software. Electronic Reseller is not entitled to
            source code for the Software.

8.    VENDOR'S WARRANTIES.

      a)    Authority. Vendor represents that it has the right and authority to
            enter into this Agreement and to grant Electronic Reseller the
            rights to the Software and Documentation granted in this Agreement.

      b)    Media. Vendor warrants to Electronic Reseller that the master media
            on which the Software is delivered to allow Electronic Reseller to
            replicate the Software is free from defects in material and
            workmanship. Vendor agrees to replace any media delivered to
            Electronic Reseller that proves defective.

      c)    Non-Infringement. Vendor warrants to Electronic Reseller that the
            Vendor has all rights, title, and interest in the product or has
            obtained the right to grant the licenses set forth in this
            Agreement. As of the execution date of the Agreement, Vendor
            represents that to the best of Vendor's knowledge the Product does
            not infringe upon or misappropriate the proprietary rights of any
            third party arising under the laws of the United States of America.

      d)    End User Warranties. Vendor will provide a warranty for the End
            Users of the Software as set forth in the End User License
            Agreement attached as Exhibit B. Electronic Reseller is not
            authorized to make any other warranties on Vendor's behalf.

9.    ELECTRONIC RESELL WARRANTIES.

      a)    Authority. Electronic Reseller represents that it has the right and
            authority to enter into this Agreement.

      b)    Replication. Electronic Reseller represents and warrants that it
            will accurately replicate the Software and Documentation, and that
            all Software distributed by the Electronic Reseller will not
            contain any viruses, worms, date bombs, time bombs, or other code
            that is specifically designed to cause the Software to cease
            operating, or to damage, interrupt, or interfere with any End
            User's Software or data.

10.   PAYMENTS.

      a)    Electronic Conversion Fee. Vendor will pay the Electronic Vendor
            Fee as specified in Exhibit C at the time of the signing of the
            Agreement. Products available from Vendor will be installed on
            Electronic Reseller's serve upon receipt of payment and fulfillment
            of other obligations made a part of this Agreement.

      b)    Amount. Electronic Reseller will pay Vendor in accordance with the
            Schedule attached hereto as Exhibit C, for each copy of a Product
            delivered to an End User by Electronic Reseller, provided, however,
            that no fee shall be due for copies of Products returned to
            Electronic Reseller for refund in accordance with the End-User
            License Agreement and accompanied by an executed Letter of
            Destruction from the End-User. Any changes to Exhibit C with
            respect to product sell price or product cost to Electronic
            Reseller must be submitted to Electronic Reseller at least thirty
            (30) days prior to the effective date.

      c)    Taxes. Electronic Reseller will pay, or require its End User
            customers to pay, all federal, state and local taxes designated,
            levied, or based upon the sale of Products by Electronic Reseller.

      d)    Payment and Reports. Within thirty (30) days after the end of each
            month, Electronic Reseller will remit to Vendor the sales fee due
            on copies of Products delivered by Electronic Reseller to End User
            customers during the immediately preceding month and provide Vendor
            with a written report (the "Report"), specifying the number of
            copies of Products that Electronic Reseller has shipped during the
            immediately prior month and the calculation of the amounts due to
            Vendor in connection therewith.

      End User Information. Electronic Reseller will provide Vendor within
      thirty (30) days after the end of each month, a report for the
      immediately prior month showing (i) the name and address of each End User
      that purchased the Product from Electronic Reseller, and (ii) the name
      and quantity of the Product purchased by the End User. Electronic
      Reseller will not share customer information with any other parties
      without the Vendors prior consent.

      e)    Book and Records. Electronic Reseller agrees to maintain adequate
            books and records relating to the distribution of Products to End
            User Customers. Such books and records shall be available at their
            place of keeping for inspection by Vendor or its representative,
            for the purpose of determining whether the correct fees have been
            paid to Vendor in accordance with the terms of this Agreement, and
            whether Electronic Reseller has otherwise compiled with the terms
            of this Agreement. Vendor shall have the right to conduct such an
            audit upon

<PAGE>   4
          ten (10) days advance notice twice each year. In the event that such
          an audit discloses an underpayment of more than five percent (5%), the
          Electronic Reseller shall pay the costs of such audit.

     f)   Failure to Pay. Any sales fee payment or part of a payment that is not
          paid when due shall bear interest at the rate of 1.5% per month from
          its due date until paid. Failure of Electronic Reseller to pay any
          fees or other charges when due shall constitute sufficient cause for
          Vendor to immediately suspend its performance hereunder and/or to
          terminate this Agreement.

11.  CONFIDENTIALITY.

          Each party agrees that all binary code, inventions, algorithms,
          know-how and ideas it obtains from the other and all other business,
          technical and financial information it obtains from the other are the
          confidential property of the disclosing party ("Confidential
          Information"). If conspicuously labeled as "proprietary" or
          "confidential" or some similar designation or, if disclosed orally or
          visually, is confirmed in writing labeled as "proprietary" or
          "confidential" or some similar designation within thirty (30) days of
          such oral or visual disclosure. All binary code (including, but not
          limited to the Software), binary documentation and underlying
          inventions, algorithms, know-how and ideas are hereby identified as
          Vendor's Confidential Information. Except as expressly and
          unambiguously allowed herein, the receiving party will hold in
          confidence and not use or disclose any Confidential Information and
          shall similarly bind its employees and contractors in writing. The
          receiving party shall not be obligated under this Section 11 with
          respect to information the receiving party can document; (1) is or has
          become readily publicly available with restriction through no fault of
          the receiving party or its employees or agents; or (2) is received
          without restriction from a third party lawfully in possession of such
          information and lawfully empowered to disclose such information; or
          (3) was rightfully in the possession of the receiving party without
          restriction prior to its disclosure by the disclosing party; or (4) is
          independently developed by the receiving party by employees without
          access to the other party's similar Confidential Information; or (5)
          is required by law or order of a court administrative agency or other
          governmental body to be disclosed by the receiving party. The parties
          obligations with respect to Confidential Information (other than with
          respect to any source code as to which the obligations shall continue
          for twenty (20 years) shall continue for the shorter of three (3)
          years from the date of termination of this Agreement or until one of
          the above enumerated conditions becomes applicable. Each party
          acknowledges that its breach of this Section 11 would cause
          irreparable injury to the other for which monetary damages are not an
          adequate remedy. Accordingly, a party will be entitled to injunctions
          and other equitable remedies in the event of such breach by the other.

12.  VENDOR TRADEMARKS.

     a)   Use. Electronic Reseller acknowledges that the Vendor Trademarks are
          trademarks owned solely and exclusively by Vendor, and agrees to use
          the Vendor Trademarks only in the form and manner and with appropriate
          legends as prescribed by Vendor. Electronic Reseller agrees not to use
          any other trademark or service mark in connection with any of the
          Vendor Trademarks without prior written approval of Vendor. All use of
          Vendor Trademarks shall inure to the benefit of Vendor.

     b)   Notices. Electronic Reseller shall not remove, alter, cover or
          obfuscate any copyright notice or other proprietary rights notice
          placed in or on the Software or Documentation by Vendor.

13.  INDEMNIFICATION.

     a)   By Vendor. Vendor will defend, indemnity and hold Electronic Reseller
          harmless from and against any and all liabilities, losses, damages,
          costs and expenses (including legal fees and expenses) associated with
          any claim or action brought against Electronic Reseller for actual or
          alleged infringement of any US patent, US copyright, US trademark, US
          service mark, trade secret, or other US proprietary rights based upon
          the duplication, sale, license, or use of the Software or
          Documentation by Electronic Reseller in accordance with this
          Agreement, provided that Electronic Reseller promptly notifies Vendor
          in writing of the claim and allows Vendor to control, and fully
          cooperates with Vendor in, the defense and all related settlement
          negotiations. Vendor shall have no liability for any settlement or
          compromise made without its consent. Upon notice of an alleged
          infringement, or if in the Vendors opinion such a claim is likely.
          Vendor shall have the right, at its option, to obtain the right for
          Electronic Reseller to continue to exercise the rights granted under
          this Agreement, substitute other software with similar operating
          capabilities, or modify the Software so that it is no longer
          infringing. The foregoing indemnification shall not apply to claims of
          infringement to the extent they arise by reason of the combination of
          the software or documentation with any other product if such claim
          would have been avoided but for such combination. In the event that
          none of the above options are reasonably available, in Vendor's sole
          opinion, Vendor may terminate
<PAGE>   5
     this Agreement.

     b)   By Electronic Reseller. Electronic Reseller shall indemnify and hold
          Vendor harmless from and against any and all liabilities, losses,
          damages, costs and expenses (including legal fees and expenses)
          associated with any claim or action brought against Vendor that may
          arise from Electronic Reseller's improper or unauthorized replication
          packaging, marketing, distribution, or installation of the Software,
          including claims based on representations warranties, or
          misrepresentations made by Electronic Reseller, or any other improper
          or unauthorized act or failure to act on the part of Electronic
          Reseller.

14.  LIMITATION OF LIABILITY. BOTH PARTIES LIABILITY SHALL BE LIMITED TO DIRECT
     DAMAGES AND EXCEPT AS PROVIDED IN THE SECTION ENTITLED "INDEMNIFICATION,"
     SHALL NOT EXCEED THE AMOUNT OF THE LICENSE FEES PAID BY ELECTRONIC RESELLER
     TO VENDOR HEREUNDER. IN NO EVENT WILL EITHER PARTY BE LIABLE FOR
     INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES (INCLUDING LOST PROFITS)
     SUFFERED BY THE OTHER PARTY, EVEN IF IT HAS PREVIOUSLY BEEN ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGES.

15.  TERM AND TERMINATION.

     a)   Term. This Agreement will continue in effect for [*] from the
          date hereof ("Initial Term"). Upon expiration of the Initial Term and
          each Renewal Term thereafter, this Agreement will be automatically
          renewed for an [*] one (1) year term ("Renewal Term") unless
          terminated by either party upon ninety (90) days' notice prior to the
          expiration of the Initial Term or any Renewal Term.

     b)   Termination for Cause. This Agreement may be terminated by a party for
          cause [*] by written notice upon the occurrence of any of the
          following events;

          i) If the other ceases to do business, or otherwise terminates its
          business operations (except as permitted under Section 16.a.) or (ii.)
          If the other shall fail to promptly secure or renew any license
          registration, permit, authorization or approval for the conduct of its
          business in the manner contemplated by this Agreement or if any such
          license, registration, permit, authorization or approval is revoked or
          suspended and not reinstated within [*]. (iii) if the other breaches
          any material provision of this Agreement and fails to fully cure such
          breach within [*] ([*] in the case of failure to pay) of written
          notice describing the breach; or (iv) If the other becomes insolvent
          or seeks protection under any bankruptcy receivership trust deed,
          creditor's arrangement composition or comparable proceeding, or if any
          such proceeding is instituted against the other and not dismissed
          within [*].

     c)   [*]

     d)   Effect of Termination. Upon termination of this Agreement for any
          reason, [*]. Electronic Reseller shall remit all Royalties and other
          fees due to Vendor within [*] of such termination.

     e)   Effect on End Users. Termination by either party will not affect the
          rights of any End User under the terms of the End-User License
          Agreement.

16.  GENERAL PROVISIONS.

     a)   Assignment. This Agreement may not be assigned by Electronic Reseller
          or by operation of law to any other person, persons, firms, or
          corporations without the express written approval of Vendor.

     b)   Notices. All notices and demands hereunder shall be in writing and
          shall be served by personal service or by mail at the address of the
          receiving party set forth in this Agreement (or at such different
          address as may be designated by such party by written notice to the
          other party). All notices and demands by mail shall be certified or
          registered mail, return receipt requested, or by nationally-recognized
          private express courier, and shall be deemed complete upon receipt.

     c)   Governing Law. This Agreement shall be governed by and construed in
          accordance with the substantive laws of the State of California.

     d)   Relationship of the Parties. Each party is acting as an Independent
          contractor and not as an agent, partner, or joint venture with the
          other party for any purpose. Except as provided in this Agreement,
          neither party shall have the right, power, or authority to act or to
          create any obligation, express or implied, on behalf of the other.

     e)   Survival of Certain Provisions. The indemnification and
          confidentiality obligations set forth in the Agreement shall survive
          the termination of the Agreement by either party for any reason.

     f)   Headings. The titles and headings of the various sections and
          paragraphs in this Agreement are intended solely for convenience of
          reference and are not intended for any other purpose whatsoever, or to
          explain, modify or

*Confidential treatment requested. Certain confidential information has been
 omitted and filed separately with the Securities and Exchange Commission.

                                                                               5
<PAGE>   6
     that it constitutes the complete and entire agreement of the parties and
     supersedes all previous communications, oral or written, and all other
     communications between them relating to the license and to the subject
     hereof. No representations or statements of any kind made by either party,
     which are not expressly stated herein, shall be binding on such party.

IN WITNESS WHEREOF, the parties have executed this Agreement as of the date set
forth above.

CYBERSOURCE CORPORATION                   MCAFEE SOFTWARE, INC. VENDOR

By:  [SIG]                                By:  /s/ PETER R. WATKINS
   ------------------------------            ------------------------------

Print Name:  [NAME]                       Print Name: Peter Watkins
           ----------------------                     ---------------------

Title:  [TITLE]                           Title:  VP & GM
      ---------------------------               ---------------------------

Date:  9/2/97                             Date:  9/11/97
     ----------------------------              ----------------------------

                                   EXHIBIT A

 I.  SOFTWARE PRODUCTS

     List all products here, with their respective suggested list price.

SEE EXHIBIT C.

II.  REQUIREMENTS CHECKLIST

The "checklist" of things needed to complete the process are:

Musts to post product- (these are things we need before your product can be
posted)

1)   Executed Electronic Reseller Agreement.

2)   Master or Gold copy of the program(s). Program(s) can be delivered to (or
     acquired by) software.net in one of the following methods. 1) on CD, 2)
     download files from Vendors FTP site, or 3) 3.5" disks (this in order of
     preference).

3)   Computer-readable electronic end-user license (.txt file). Please include
     as a separate file, it takes extra time to pull ones from the install
     process.

4)   Computer-readable product documentation (.pdf or .txt file). (if
     documentation is to be included)

5)   A range of 100 license numbers (if the product is serialized).

6)   Fill out the template located in Exhibit D for each product. IMPORTANT.
     This is the information used by software.net webmasters to post your
     products. Identify all punctuation clearly so we can get it right the first
     time.

Should Have's, but not essential to products being added to site:

7)   Computer-readable product specification sheet, collateral, or other
     information (html, .pdf or .txt file). We can also pull
<PAGE>   7
     this information from your web site if available. Notify us to the method
     you wish to provide us the data and the appropriate locations.

8)   Trademarks/logos (.gif file).

Products will be converted for electronic distribution by CyberSource
Corporation. Product conversion includes packaging the product in CyberSource's
secure and encrypted packaging container, inclusion in the software.net online
catalog, and posting of product information provided by vendor in HTML format.

Send to CyberSource Corporation, Attention: software.net Marketing, 550 South
Winchester Blvd., Suite 301, San Jose, CA 95128.
<PAGE>   8

                                   EXHIBIT B

END-USER LICENSE AGREEMENT

NOTICE TO USERS: CAREFULLY READ THE FOLLOWING LEGAL AGREEMENT. USE OF ANY OF
THE SOFTWARE PROVIDED WITH THIS AGREEMENT (THE "SOFTWARE") CONSTITUTES YOUR
ACCEPTANCE OF THESE TERMS. IF YOU DO NOT AGREE TO THE TERMS OF THIS AGREEMENT
WITH RESPECT TO ANY OF THE SOFTWARE PROVIDED, PROMPTLY REMOVE THE SOFTWARE
TOGETHER WITH ALL COPIES FROM YOUR COMPUTER AND RETURN IT AND THE ACCOMPANYING
ITEMS (INCLUDING WRITTEN MATERIALS AND PACKAGING) TO THE LOCATION WHERE YOU
OBTAINED THEM FOR A REFUND. REGISTERING YOUR PRODUCT WITH MCAFEE SOFTWARE, INC.
("MCAFEE"), WILL IMPROVE COMMUNICATIONS WITH MCAFEE. A Registration form is
located below. [If you purchased the product directly from McAfee, you are
already registered.]

1. LICENSE GRANT. McAfee and its suppliers grant to you a non-exclusive,
non-transferable right to use the SOFTWARE on file servers connected to a
maximum number of user computers, or on a maximum number of user computers, not
exceeding the number of user computers specified on the packaging for this
product. If the media upon which the SOFTWARE is received by you contains
versions of the SOFTWARE for different operating systems (e.g. VirusScan for
OS/2 and VirusScan for Windows 95), then you may only use the version of the
SOFTWARE applicable to the operating system used on the user computer for which
the SOFTWARE is licensed; provided, however, that any license to use VirusScan
for Windows 3.1x and VirusScan for Windows 95 also includes a license to use
VirusScan for DOS. You agree you will only copy the SOFTWARE into any
machine-readable or printed form as necessary to use it in accordance with this
license or for backup purposes in support of your use of the SOFTWARE.

This license is effective until terminated. You may terminate it at any point
by destroying the SOFTWARE together with all copies of the SOFTWARE. Also,
McAfee has the option to terminate if you fail to comply with any term or
condition of this Agreement. You agree upon such termination to destroy the
SOFTWARE together with all copies of the SOFTWARE.

2. UPGRADES. This license is limited to the version of the SOFTWARE enclosed
and does not include the right to upgrades except as provided in this Section
2. If you purchased this software from a retail store or directly from McAfee,
you are entitled: (a) as to products other than VirusScan Deluxe, to download
and use all upgrades of the SOFTWARE (including virus signature files (DAT
files)) released during the one year period following purchase; and (b) as to
VirusScan Deluxe, to download and use all upgrades of the SOFTWARE (including
virus signature

<PAGE>   9
files (DAT files)) released during the two year period following purchase. If
you receive the SOFTWARE packaged with PC hardware or software not purchased
from McAfee, you are entitled to one free electronic update of the SOFTWARE. If
the PC hardware with which the SOFTWARE was received was purchased for
individual or home use, then you are further entitled to download and use all
upgrades of the SOFTWARE (including virus signature files (DAT files)) released
during the three month period following purchase. If the PC hardware with which
the SOFTWARE was received was purchased for business use, then you may download
and use all upgrades of the SOFTWARE (including virus signature files (DAT
files)) released during the three month period following purchase upon
obtaining a corporate password from McAfee. You must in any event register with
McAfee to receive upgrades hereunder.

3. COPYRIGHT. The SOFTWARE is protected by United States copyright law and
international treaty provisions. You acknowledge that no title to the
intellectual property in the SOFTWARE is transferred to you. You further
acknowledge that title and full ownership rights to the SOFTWARE will remain
the exclusive property of McAfee or its suppliers, and you will not acquire any
rights to the SOFTWARE except as expressly set forth in this license. You agree
that any copies of the SOFTWARE will contain the same proprietary notices which
appear on and in the SOFTWARE.

4. REVERSE ENGINEERING. You agree that you will not attempt to reverse compile,
modify, translate, or disassemble the SOFTWARE in whole or in part.

5. LIMITED WARRANTY. For 30 days from the date of shipment, we warrant that the
media (for example diskettes) on which the SOFTWARE is contained will be free
from defects in materials and workmanship.

6. CUSTOMER REMEDIES. If the SOFTWARE does not conform to the limited warranty
in Section 5 above ("Limited Warranty"), your sole remedy shall be to return
the media with a description of the problem to McAfee. The defective media in
which the SOFTWARE is contained will be replaced by McAfee at no additional
charge to you. If you do not receive media which is free from defects and
materials and workmanship during the 60-day warranty period, McAfee will refund
to you the amount you paid for the SOFTWARE. The Limited Warranty is void if
failure of the SOFTWARE has resulted from accident or from abuse or
misapplication by you. Any replacement SOFTWARE will be warranted for the
remainder of the original Limited Warranty period.

7. NO OTHER WARRANTIES, NEITHER McAFEE NOR ITS SUPPLIERS WARRANT THAT THE
SOFTWARE IS ERROR FREE, EXCEPT FOR THE EXPRESS LIMITED WARRANTY IN SECTION 5
("LIMITED WARRANTY"). McAFEE AND ITS SUPPLIERS DISCLAIM ALL OTHER WARRANTIES
WITH RESPECT TO THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND
<PAGE>   10
NONINFRINGEMENT OF THIRD PARTY RIGHTS.

SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OF IMPLIED WARRANTIES OR
LIMITATIONS ON HOW LONG AN IMPLIED WARRANTY MAY LAST, OR THE EXCLUSION OR
LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES. SO THE ABOVE LIMITATIONS OR
EXCLUSIONS MAY NOT APPLY TO YOU. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS
AND YOU MAY ALSO HAVE OTHER RIGHTS WHICH VARY FROM JURISDICTION TO JURISDICTION.

8. SEVERABILITY. In the event of invalidity of any provision of this license,
the parties agree that such invalidity shall not affect the validity of the
remaining portions of this license.

9. NO LIABILITY FOR CONSEQUENTIAL DAMAGES. IN NO EVENT SHALL McAFEE OR ITS
SUPPLIERS BE LIABLE TO YOU FOR ANY CONSEQUENTIAL, SPECIAL, INCIDENTAL, OR
INDIRECT DAMAGES OF ANY KIND ARISING OUT OF THE DELIVERY, PERFORMANCE OR USE OF
THE SOFTWARE, EVEN IF McAFEE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
DAMAGES. IN NO EVENT WILL McAFEE'S OR ITS SUPPLIERS' LIABILITY FOR ANY CLAIMS,
WHETHER IN CONTRACT, TORT OR ANY OTHER THEORY OF LIABILITY, EXCEED, IN THE
AGGREGATE THE LICENSE FEE PAID BY YOU, IF ANY.

10. GOVERNING LAW. This license will be governed by the internal laws of the
State of California. The United Nations Convention on Contracts for the
International Sale of Goods is specifically disclaimed.

11. ENTIRE AGREEMENT. This is the entire agreement between you and McAfee and
its suppliers which supersedes any prior agreement or understanding, whether
written or oral, relating to the subject matter of this license.

12. NetRemote users are licensed to use the SOFTWARE on one LAN connected user
computer. Additionally, users are licensed to use the SOFTWARE on a maximum
number of 2 user computers connected by an asynchronous/modem connection.

U.S. GOVERNMENT RESTRICTED RIGHTS

Any distribution or license of the SOFTWARE to the U.S. Government or its
agencies or instrumentalities (the "Government") is made only with RESTRICTED
RIGHTS. Use, duplication or disclosure by the Government is subject to
restriction as set forth in subparagraph (c)(1)(ii) of the Rights in Technical
Data and Computer Software clause at DFAR 252.227-7013, or as set forth in the
particular department or agency regulations or rules which provide McAfee
protection equivalent to or greater than the above-cited clause.
Contractor/Manufacturer is McAfee Software, Inc. 2805 Bowers Avenue, Santa
Clara, California 95051-0963.

Should you have any questions concerning this license agreement, or if you
desire to contact McAfee for any reason, please call (408) 988-3832, fax (408)
970-9727, or write: McAfee Software, Inc. 2805 Bowers Avenue,
<PAGE>   11
Santa Clara, California 95051-0963. McAfee Associates, Inc. is considered a
Supplier for purposes of this License.

<PAGE>   12

                                                                       Exhibit C

Sales Fee Schedule sold at Software.Net (see notes below)

<TABLE>
<CAPTION>
PRODUCT NAME        PLATFORM       SRP          ELP          COST
------------        --------       ---         ----          ----
<S>                 <C>           <C>          <C>          <C>
VirusScan           WIN95         $[*]         $[*]         $[*]
                    WIN 3.1X      $[*]         $[*]         $[*]
                    NT            $[*]         $[*]         $[*]
                    DOS           $[*]         $[*]         $[*]

PCCrypto            WIN95         $[*]         $[*]         $[*]

QuickBackup         WIN95/NT      $[*]         $[*]         $[*]

PC Medic 97         WIN95/NT      $[*]         $[*]         $[*]

WebScanX            WIN95/NT      $[*]         $[*]         $[*]
</TABLE>

Sales Fee Schedule sold at NetScape.com hosted by Software.Net (see notes below)

<TABLE>
<CAPTION>
PRODUCT NAME        PLATFORM       SRP          ELP          COST
------------        --------       ---         ----          ----
<S>                 <C>           <C>          <C>          <C>
VirusScan           WIN95         $[*]         $[*]         $[*]
                    WIN 3.1X      $[*]         $[*]         $[*]
                    NT            $[*]         $[*]         $[*]
                    DOS           $[*]         $[*]         $[*]

PCCrypto            WIN95         $[*]         $[*]         $[*]

QuickBackup         WIN95/NT      $[*]         $[*]         $[*]

PC Medic 97         WIN95/NT      $[*]         $[*]         $[*]

WebScanX            WIN95/NT      $[*]         $[*]         $[*]
</TABLE>

Notes:

1.   SRP - The suggested published list price for boxed product sold into
     retail stores, determined by the Vendor.

2.   ELP - (Electronic List Price) - The list price for the Electronic version.
     [*] 10 to 20% less than the box version.

3.   Cost - This is what Electronic Reseller will pay vendor for each copy of
     product distributed.

Annual product maintenance fee(1):
Covers one full year of product updates and releases.

Total product maintenance fees due software.net(2) = [*]
*Marketing Plan Description:

At launch:

- Large promotion space (1 wk) on software.net homepage for the initial launch.

- Rotating banner on the homepage for 1st quarter.

- Listing in Cool Deals section (1 wk).

*Confidential treatment requested. Certain confidential information has been
 omitted and filed separately with the Securities and Exchange Commission.

<PAGE>   13
Ongoing commitment through 1997 if McAfee products stay in top 5:
-Top promotional spot in at least one open center each week.
-Continuing of rotating banner on software.net homepage.

Marketing Plan Fee Fee waived

1-All Annual product maintenance fees can be applied to a sponsorship program
within the first thirty (30) days of this agreement. See marketing kit for
details of sponsorship opportunities.

2-software.net will invoice this amount which is due and payable at time of
signed agreement. This is a payment for services to be performed and
software.net will not perform such services until payment has been received.

                                   Exhibit D

Please fill out the following template for each product (as you wish it to
appear in software.net):

Vendor Name (up to 36 characters): McAfee Software, Inc.

Product Name (include version number): To be provided with each version
                                       supplied (TPB)
Does this product come with electronic documentation? Yes   online help ? Yes
What platform(s) does this product run under?  (TPB)

What is the approximate box street price of this product?  See Exhibit C

What is the approximate ESD street price of this product-The price software.net
will sell product for (10-20% less than the box street price)  See Exhibit C

What is software.net's cost  See Exhibit C

What, if any, is the vendor part number of this product?  (TPB)

Is this product serialized?:  NO if yes, have serial numbers been provided? ____

Does this product have an export ban? (TPB) ____ If yes, to which countries is
export restricted or banned?

______________________________________________________________________________

Name of business/marketing contact:  [*]

Phone Number: __________________ Email Address: [*]

Name of technical contact (to call if trouble with preparing products): _______

Phone Number: __________________ Email Address: [*]

Name of person to receive monthly reports via email:  Philip Artt

Phone Number: (972) 855-2547     Email

Address: philip artt@cc.mcafee.com

From the category listing below, enter one (1) category this product fits into:
(TPB)

                                                  1541.Operating System Software

*Confidential treatment requested. Certain confidential information has been
 omitted and filed separately with the Securities and Exchange Commission.
<PAGE>   14

<TABLE>
<S>                                                      <C>
1501.  Spreadsheet Software                              1543.  Programming and Languages Utilities
1503.  Database Software                                 1545.  Memory Manager Software
1505.  Wordprocessor Software                            1547.  File Conversion & File Transfer Software
1507.  Suites & Integrated Software Packages             1549.  Reference & Information Software
1509.  Desktop Publishing Software                       1551.  Education & Entertainment Software
1511.  Communications Software                           1553.  Games & Entertainment Software
1512.  Internet Software                                 1555.  Voice Recognition Software
1513.  Fax, OCR & Document Imaging Software              1561.  Forms Generator, Designer & filler
1515.  E-Mail, Groupware & Video Conference Software     1563.  Back-up Software
1517.  Terminal Emulation Software                       1565.  Menu S/W & Desktop Organizers
1521.  Graphics & Presentation Graphics Software         1567.  Virus Detection Software
1523.  CAD Software                                      1569.  Security Software
1525.  Multimedia Software                               1571.  Diagnostic Software
1527.  Clip Art, Symbol & Image Libraries                1573.  Screen Saver Software
1529.  Font Software                                     1575.  Printer Utility Software
1531.  Accounting Software                               1577.  Network Mgmt & Utility Software
1533.  Tax Software                                      1579.  General Utility Software
1535.  Statistics Software                               9900.  Information
1537.  Project & Time Management Software                9901.  Electronic Books
1539.  General Business Software
</TABLE><PAGE>   1
                                                                    EXHIBIT 4.11

                         COMMON STOCK PURCHASE AGREEMENT

                          DATED AS OF JANUARY 11, 2000

                                 BY AND BETWEEN

                                     AVIRON

                                       AND

                                ACQUA WELLINGTON
                       NORTH AMERICAN EQUITIES FUND, LTD.

<PAGE>   2

                         COMMON STOCK PURCHASE AGREEMENT

        This COMMON STOCK PURCHASE AGREEMENT (this "Agreement") is dated as of
January 11, 2000 by and between Aviron, a Delaware corporation (the "Company")
and Acqua Wellington North American Equities Fund, Ltd., a company organized
under the laws of the Commonwealth of The Bahamas (the "Purchaser").

        The parties hereto agree as follows:

                                    ARTICLE 1

                                   DEFINITIONS

               SECTION 1.1   Definitions.

               (a) "Commission" shall have the meaning assigned to such term in
Section 2.3 hereof.

               (b) "Commission Documents" shall have the meaning assigned to
such term in Section 3.1(f) hereof.

               (c) "Commission Filings" means the Company's Form 10-K for the
fiscal year ended December 31, 1998, Registration Statement on Form S-3 No.
333-87185, and all other filings made by the Company after the date hereof
pursuant to the Securities Exchange Act of 1934.

               (d) "Draw Down Amount" means the actual amount of a Draw Down up
to $4,000,000.

               (e) "Draw Down Discount Price" means (i) 95% of the VWAP if on
any trading day during the Draw Down Pricing Period, the VWAP of the Common
Stock is equal to or exceeds $18.00; (ii) 94% of the VWAP if on any trading day
during the Draw Down Pricing Period, the VWAP of the Common Stock is equal to or
exceeds $15.00 but is less than $18.00; (iii) 93% of the VWAP if on any trading
day during the Draw Down Pricing Period, the VWAP of the Common Stock is equal
to or exceeds $12.00 but is less than $15.00; and (iv) 92% of the VWAP if on any
trading day during the Draw Down Pricing Period, the VWAP of the Common Stock is
equal to or exceeds $10.00 but is less than $12.00.

               (f) "Draw Down Notice" shall have the meaning assigned to such
term in Section 6.1(j) hereof.

               (g) "Draw Down Pricing Period" shall mean a period of eighteen
(18) consecutive trading days following a Draw Down Notice.

               (h) "Effective Date" shall mean the date the Registration
Statement of the Company covering the Shares being subscribed for hereby is
declared effective.

                                        1
<PAGE>   3

               (i) "Material Adverse Effect" shall mean any effect on the
business, results of operations, assets or financial condition of the Company
that is material and adverse to the Company and its subsidiaries, taken as a
whole and/or any condition, circumstance, or situation that would prohibit the
Company from entering into and performing any of its obligations under this
Agreement in any material respect.

               (j) "Material Change in Ownership" shall mean that the officers
and directors of the Company shall beneficially own in the aggregate less than
2% of the outstanding Common Stock of the Company that the officers and
directors beneficially own as of the date hereof.

               (k) "Prospectus" as used in this Agreement means the prospectus
in the form included in the Registration Statement, or, if the prospectus
included in the Registration Statement omits information in reliance on Rule
430A under the Securities Act of 1933, as amended, and the rules and regulations
of the Commission thereunder (collectively, the "Securities Act"), and such
information is included in a prospectus filed with the Commission pursuant to
Rule 424(b) under the Securities Act, the term "Prospectus" as used in this
Agreement means the prospectus in the form included in the Registration
Statement as supplemented by the addition of the Rule 430A information contained
in the prospectus filed with the Commission pursuant to Rule 424(b).

               (l) "Registration Statement" shall mean the registration
statement on Form S-3, Commission File Number 333-87185 under the Securities
Act, filed with the Securities and Exchange Commission for the registration of
the Shares, as such Registration Statement may be amended from time to time.

               (m) "Settlement Date" shall have the meaning assigned to such
term in Section 6.1(d) hereof.

               (n) "Shares" shall mean the shares of Common Stock of the Company
being purchased hereunder.

               (o) "Threshold Price" is the lowest VWAP at which the Company
will sell Shares during each Draw Down Pricing Period.

               (p) "VWAP" shall mean the daily volume weighted average price
(based on a trading day from 9:30 a.m. to 4:00 p.m., E.S.T.) of the Company
on NASDAQ (or any successor thereto) as reported by Bloomberg Financial LP using
the AQR function.

                                   ARTICLE 2

                        PURCHASE AND SALE OF COMMON STOCK

        SECTION 2.1 Purchase and Sale of Stock. Subject to the terms and
conditions of this Agreement, the Company shall issue and sell to the Purchaser
and the Purchaser shall purchase from the Company up to $48,000,000 of the
Company's common stock, $.001 par value per share (the "Common Stock"), based on
up to Draw Downs of up to $4,000,000 per Draw Down. In no event shall the amount
of Common Stock purchased by the Purchaser exceed $4,000,000 per Draw Down.

                                       2
<PAGE>   4

        SECTION 2.2 The Shares. The Company has authorized and has reserved and
covenants to continue to reserve, subject to Section 4.5(b) hereof, free of
preemptive rights and other similar contractual rights of stockholders, a
sufficient number of its authorized but unissued shares of its Common Stock to
cover the Shares to be issued in connection with all Draw Downs.

        SECTION 2.3 Registration Statement and Prospectus. The Company has
prepared and filed with the Securities and Exchange Commission (the
"Commission") in accordance with the provisions of the Securities Act, the
Registration Statement, including a prospectus subject to completion relating to
the Shares. The Registration Statement was declared effective on October 8,
1999.

        SECTION 2.4 Purchase Price and Closing. The Company agrees to issue and
sell to the Purchaser and, in consideration of and in express reliance upon the
representations, warranties, covenants, terms and conditions of this Agreement,
the Purchaser, agrees to purchase that number of the Shares to be issued in
connection with each Draw Down. The closing of the execution and delivery of
this Agreement shall take place at the offices of Parker Chapin Flattau &
Klimpl, LLP 1211 Avenue of the Americas, New York, NY 10036 (the "Closing") at
8:00 a.m. E.S.T. on (i) January 12, 2000, or (ii) such other time and place or
on such date as the Purchaser and the Company may agree upon (the "Closing
Date"). Each party shall deliver all documents, instruments and writings
required to be delivered by such party pursuant to this Agreement at or prior to
the Closing.

                                   ARTICLE 3

                         REPRESENTATIONS AND WARRANTIES

        SECTION 3.1 Representation and Warranties of the Company. The Company
hereby makes the following representations and warranties to the Purchaser:

               (a) Organization, Good Standing and Power. The Company is a
corporation duly incorporated, validly existing and in good standing under the
laws of Delaware and has the requisite corporate power to own, lease and operate
its properties and assets and to conduct its business as it is now being
conducted. As of the date hereof, the Company does not have any subsidiaries (as
defined in Section 3.1(g)) except as set forth in the Registration Statement and
in the Company's most recent Form 10-K, including the accompanying financial
statements (the "Form 10-K"), or in the Company's most recent Form 10-Q (the
"Form 10-Q"), or on Schedule 3.1(a) attached hereto. The Company and each such
subsidiary is duly qualified as a foreign corporation to do business and is in
good standing in every jurisdiction in which the nature of the business
conducted or property owned by it makes such qualification necessary except for
any jurisdiction in which the failure to be so qualified will not have a
Material Adverse Effect.

               (b) Authorization; Enforcement. The Company has the requisite
corporate power and authority to enter into and perform this Agreement and to
issue and sell the Shares in accordance with the terms hereof. The execution,
delivery and performance of this Agreement by the Company and the consummation
by it of the transactions contemplated hereby have been duly and validly
authorized by all necessary corporate action, and, except as contemplated by
Section 4.5(b), no further consent or authorization of the Company or its Board
of Directors or stockholders is required. This Agreement has been duly executed
and delivered by the

                                        3
<PAGE>   5
Company. This Agreement constitutes, or shall constitute when executed and
delivered, a valid and binding obligation of the Company enforceable against the
Company in accordance with its terms, except as such enforceability may be
limited by applicable bankruptcy, insolvency, reorganization, moratorium,
liquidation, conservatorship, receivership or similar laws relating to, or
affecting generally the enforcement of, creditor's rights and remedies or by
other equitable principles of general application.

               (c) Capitalization. The authorized capital stock of the Company
and the shares thereof issued and outstanding as of the date hereof are set
forth in the Registration Statement or on Schedule 3.1(c) attached hereto. All
of the outstanding shares of the Company's Common Stock have been duly and
validly authorized, and are fully paid and non-assessable. Except as set forth
in this Agreement or as set forth in the Registration Statement, the Commission
Documents, the Commission Filings or on Schedule 3.1(c) attached hereto, as of
the date hereof, no shares of Common Stock are entitled to preemptive rights or
registration rights and there are no outstanding options, warrants, scrip,
rights to subscribe to, call or commitments of any character whatsoever relating
to, or securities or rights convertible into, any shares of capital stock of the
Company. Furthermore, except as set forth in this Agreement, the Registration
Statement, the Commission Documents or the Commission Filings or on Schedule
3.1(c) attached hereto, as of the date hereof, there are no contracts,
commitments, understandings, or arrangements by which the Company is or may
become bound to issue additional shares of the capital stock of the Company or
options, securities or rights convertible into shares of capital stock of the
Company. Except for customary transfer restrictions contained in agreements
entered into by the Company in order to sell restricted securities or as
described in the Registration Statement, the Commission Documents or the
Commission Filings, or on Schedule 3.1(c) attached hereto, as of the date
hereof, the Company is not a party to any agreement granting registration rights
to any person with respect to any of its equity or debt securities. Except as
set forth in the Registration Statement, the Commission Documents or the
Commission Filings or on Schedule 3.1(c) attached hereto, as of the date hereof,
the Company is not a party to, and it has no knowledge of, any agreement
restricting the voting or transfer of any shares of the capital stock of the
Company. Except as set forth in the Registration Statement, the Commission
Documents or the Commission Filings or on Schedule 3.1(c) attached hereto, the
offer and sale of all capital stock, convertible securities, rights, warrants,
or options of the Company issued prior to the Closing complied with all
applicable federal and state securities laws, and no stockholder has a right of
rescission or damages with respect thereto which would have a Material Adverse
Effect. The Company has furnished or made available to the Purchaser true and
correct copies of the Company's Certificate of Incorporation as in effect on the
date hereof (the "Articles"), and the Company's Bylaws as in effect on the date
hereof (the "Bylaws").

               (d) Issuance of Shares. The Shares to be issued under this
Agreement have been duly authorized by all necessary corporate action and, when
paid for or issued in accordance with the terms hereof, the Shares shall be
validly issued and outstanding, fully paid and non-assessable, and the Purchaser
shall be entitled to all rights accorded to a holder of Common Stock.

               (e) No Conflicts. Except as disclosed on Schedule 3.1(e) attached
hereto, the execution, delivery and performance of this Agreement by the Company
and the consummation by the Company of the transactions contemplated therein do
not (i) violate any provision of the Company's Articles or Bylaws, (ii) conflict
with, or constitute a default (or an event which with

                                        4
<PAGE>   6

notice or lapse of time or both would become a default) under, or give to others
any rights of termination, amendment, acceleration or cancellation of, any
material agreement, mortgage, deed of trust, indenture, note, bond, license,
lease agreement, instrument or obligation to which the Company is a party, (iii)
create or impose a lien, charge or encumbrance on any property of the Company
under any agreement or any commitment to which the Company is a party or by
which the Company is bound or by which any of its respective properties or
assets are bound, or (iv) result in a violation of any federal, state, local or
foreign statute, rule, regulation, order, judgment or decree (including federal
and state securities laws and regulations) applicable to the Company or any of
its subsidiaries or by which any property or asset of the Company or any of its
subsidiaries are bound or affected, except, in all cases, for such conflicts,
defaults, terminations, amendments, acceleration, cancellations and violations
as would not, individually or in the aggregate, have a Material Adverse Effect.
The Company is not required under federal, state or local law, rule or
regulation to obtain any consent, authorization or order of, or make any filing
or registration with, any court or governmental agency in order for it to
execute, deliver or perform any of its obligations under this Agreement, or
issue and sell the Shares in accordance with the terms hereof (other than any
filings which may be required to be made by the Company with the Commission, or
Nasdaq subsequent to the Closing, and, any registration statement which may be
filed pursuant hereto); provided that, for purpose of the representation made in
this sentence, the Company is assuming and relying upon the accuracy of the
relevant representations and agreements of the Purchaser herein.

               (f) Commission Documents, Financial Statements. The Common Stock
of the Company is registered pursuant to Section 12(b) or 12(g) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), and, except as
disclosed in the Registration Statement, or the Commission Documents or the
Commission Filings or on Schedule 3.1(f) attached hereto, as of the date hereof,
the Company has timely filed all reports, schedules, forms, statements and other
documents required to be filed by it with the Commission pursuant to the
reporting requirements of the Exchange Act, including material filed pursuant to
Section 13(a) or 15(d) of the Exchange Act (all of the foregoing including
filings incorporated by reference therein being referred to herein as the
"Commission Documents"). The Company has delivered or made available to the
Purchaser true and complete copies of the Commission Documents filed with the
Commission since December 31, 1998 and prior to the Closing Date. The Company
has not provided to the Purchaser any information which, according to applicable
law, rule or regulation, should have been disclosed publicly by the Company but
which has not been so disclosed, other than with respect to the transactions
contemplated by this Agreement. As of their respective dates, the Form 10-K for
the year ended December 31, 1998 complied in all material respects with the
requirements of the Exchange Act and the rules and regulations of the Commission
promulgated thereunder and other federal, state and local laws, rules and
regulations applicable to such documents, and, as of their respective dates,
such Form 10-K did not contain any untrue statement of a material fact or omit
to state a material fact required to be stated therein or necessary in order to
make the statements therein, in light of the circumstances under which they were
made, not misleading. The financial statements of the Company included in the
Commission Documents comply as to form in all material respects with applicable
accounting requirements and the published rules and regulations of the
Commission or other applicable rules and regulations with respect thereto. Such
financial statements have been prepared in accordance with generally accepted
accounting principles ("GAAP") applied on a consistent basis during the periods
involved (except (i) as may be otherwise indicated in such financial statements
or the notes thereto or (ii) in the case of unaudited interim statements, to the
extent

                                        5
<PAGE>   7

they may not include footnotes or may be condensed or summary statements), and
fairly present in all material respects the financial position of the Company
and its subsidiaries as of the dates thereof and the results of operations and
cash flows for the periods then ended (subject, in the case of unaudited
statements, to normal year-end audit adjustments).

               (g) Subsidiaries. The Commission Documents or Schedule 3.1(g)
attached hereto set forth each subsidiary of the Company as of the date hereof,
showing the jurisdiction of its incorporation or organization and showing the
percentage of each person's ownership of the outstanding stock or other
interests of such subsidiary. For the purposes of this Agreement, "subsidiary"
shall mean any corporation or other entity of which at least a majority of the
securities or other ownership interest having ordinary voting power (absolutely
or contingently) for the election of directors or other persons performing
similar functions are at the time owned directly or indirectly by the Company
and/or any of its other subsidiaries. Except as set forth in the Commission
Documents or the Commission Filings, none of such subsidiaries is a "significant
subsidiary" as defined in Regulation S-X.

               (h) No Material Adverse Change. Since September 30, 1999, the
Company has not experienced or suffered any
Material Adverse Effect.

               (i) No Undisclosed Liabilities. Except as disclosed in the
Commission Documents or the Commission Filings or on Schedule 3.1(i) attached
hereto, neither the Company nor any of its subsidiaries has any liabilities,
obligations, claims or losses (whether liquidated or unliquidated, secured or
unsecured, absolute, accrued, contingent or otherwise) that would be required to
be disclosed on a balance sheet of the Company or any subsidiary (including the
notes thereto) in conformity with GAAP not disclosed in the Commission
Documents, other than those incurred in the ordinary course of the Company's or
its subsidiaries respective businesses since December 31, 1998 and which,
individually or in the aggregate, do not or would not have a Material Adverse
Effect.

               (j) No Undisclosed Events or Circumstances. No event or
circumstance has occurred or exists with respect to the Company or its
subsidiaries or their respective businesses, properties, prospects, operations
or financial condition, which, under applicable law, rule or regulation,
requires public disclosure or announcement by the Company but which has not been
so publicly announced or disclosed and which, individually or in the aggregate,
do not or would not have a Material Adverse Effect.

               (k) Indebtedness. Schedule 3.1(k) sets forth as of December 31,
1999 all outstanding secured and unsecured Indebtedness of the Company or any
subsidiary, or for which the Company or any subsidiary has commitments. For the
purposes of this Agreement, "Indebtedness" shall mean (a) any liabilities for
borrowed money or amounts owed in excess of $100,000 (other than trade accounts
payable incurred in the ordinary course of business), (b) all guaranties,
endorsements and other contingent obligations in respect of Indebtedness of
others, whether or not the same are or should be reflected in the Company's
balance sheet (or the notes thereto), except guaranties by endorsement of
negotiable instruments for deposit or collection or similar transactions in the
ordinary course of business; and (c) the present value of any lease payments in
excess of $100,000 due under leases required to be capitalized in accordance
with GAAP. Neither the Company nor any subsidiary is in default with respect to
any Indebtedness.

                                        6
<PAGE>   8

               (l) Title to Assets. Each of the Company and the subsidiaries has
good and marketable title to all of its real and personal property reflected in
the Commission Documents, free of any mortgages, pledges, charges, liens,
security interests or other encumbrances, except for those indicated in the
Commission Documents, the Commission Filings or on Schedule 3.1(l) attached
hereto or such that could not reasonably be expected to cause a Material Adverse
Effect. All said leases of the Company and each of its subsidiaries are valid
and subsisting and in full force and effect in all material respects.

               (m) Actions Pending. There is no action, suit, claim,
investigation or proceeding pending or, to the knowledge of the Company,
threatened against the Company or any subsidiary which questions the validity of
this Agreement or the transactions contemplated hereby or any action taken or to
be taken pursuant hereto or thereto. Except as set forth in the Commission
Documents or the Commission Filings or on Schedule 3.1(m) attached hereto, there
is no action, suit, claim, investigation or proceeding pending or, to the
knowledge of the Company, threatened, against or involving the Company, any
subsidiary or any of their respective properties or assets and which, if
adversely determined, is reasonably likely to result in a Material Adverse
Effect.

               (n) Compliance with Law. The business of the Company and the
subsidiaries has been and is presently being conducted in accordance with all
applicable federal, state and local governmental laws, rules, regulations and
ordinances, except as set forth in the Commission Documents or the Commission
Filings or on Schedule 3.1(n) attached hereto or such that do not cause a
Material Adverse Effect. The Company and each of its subsidiaries have all
franchises, permits, licenses, consents and other governmental or regulatory
authorizations and approvals necessary for the conduct of its business as now
being conducted by it unless the failure to possess such franchises, permits,
licenses, consents and other governmental or regulatory authorizations and
approvals, individually or in the aggregate, could not reasonably be expected to
have a Material Adverse Effect.

               (o) Certain Fees. Except as set forth on Schedule 3.1(o) attached
hereto, no brokers, finders or financial advisory fees or commissions will be
payable by the Company or any subsidiary with respect to the transactions
contemplated by this Agreement.

               (p) Disclosure. To the best of the Company's knowledge, neither
this Agreement or the Schedules hereto nor any other documents, certificates or
instruments furnished to the Purchaser by or on behalf of the Company or any
subsidiary in connection with the transactions contemplated by this Agreement
contain any untrue statement of a material fact or omits to state a material
fact necessary in order to make the statements made herein or therein, in the
light of the circumstances under which they were made herein or therein, not
misleading.

               (q) Operation of Business. The Company or one of the subsidiaries
owns or possesses all patents, trademarks, service marks, trade names,
copyrights, licenses and authorizations as set forth in the Commission Documents
or the Commission Filings or on Schedule 3.1(q) attached hereto and all rights
with respect to the foregoing, which are necessary for the conduct of its
business as now conducted without any conflict with the rights of others, except
to the extent set forth in the Commission Documents or that a Material Adverse
Effect could not reasonably be expected to result from such conflict.

                                        7
<PAGE>   9

               (r) Environmental Compliance. Except as disclosed in the
Commission Filings or on Schedule 3.1(r) attached hereto, the Company and each
of its subsidiaries have obtained all material approvals, authorization,
certificates, consents, licenses, orders and permits or other similar
authorizations of all governmental authorities, or from any other person, that
are required under any Environmental Laws. "Environmental Laws" shall mean all
applicable laws relating to the protection of the environment including, without
limitation, all requirements pertaining to reporting, licensing, permitting,
controlling, investigating or remediating emissions, discharges, releases or
threatened releases of hazardous substances, chemical substances, pollutants,
contaminants or toxic substances, materials or wastes, whether solid, liquid or
gaseous in nature, into the air, surface water, groundwater or land, or relating
to the manufacture, processing, distribution, use, treatment, storage, disposal,
transport or handling of hazardous substances, chemical substances, pollutants,
contaminants or toxic substances, material or wastes, whether solid, liquid or
gaseous in nature. Except for such instances as would not individually or in the
aggregate have a Material Adverse Effect, to the best of the Company's
knowledge, there are no past or present events, conditions, circumstances,
incidents, actions or omissions relating to or in any way affecting the Company
or its subsidiaries that violate or could reasonably be expected to violate any
Environmental Law after the Closing or that could reasonably be expected to give
rise to any environmental liability, or otherwise form the basis of any claim,
action, demand, suit, proceeding, hearing, study or investigation (i) under any
Environmental Law, or (ii) based on or related to the manufacture, processing,
distribution, use, treatment, storage (including without limitation underground
storage tanks), disposal, transport or handling, or the emission, discharge,
release or threatened release of any hazardous substance.

               (s) Material Agreements. Except as set forth in the Commission
Documents or on Schedule 3.1(s) attached hereto, neither the Company nor any
subsidiary is a party to any written or oral contract, instrument, agreement,
commitment, obligation, plan or arrangement, a copy of which would be required
to be filed with the Commission as an exhibit to a registration statement on
Form S-3 or applicable form (collectively, "Material Agreements") if the Company
or any subsidiary were registering securities under the Securities Act. The
Company and each of its subsidiaries has in all material respects performed all
the obligations required to be performed by them to date under the foregoing
agreements, have received no notice of default and, to the best of the Company's
knowledge are not in default under any Material Agreement now in effect, the
result of which could reasonably be expected to cause a Material Adverse Effect.

               (t) Transactions with Affiliates. Except as set forth in the
Commission Documents or the Commission Filings or on Schedule 3.1(t) attached
hereto, there are no loans, leases, agreements, contracts, royalty agreements,
management contracts or arrangements or other continuing transactions exceeding
$100,000 between (a) the Company, any subsidiary or any of their respective
customers (excluding agreements related to the purchase or lease of the
Company's products) or suppliers on the one hand, and (b) on the other hand, any
officer, employee, consultant or director of the Company, or any of its
subsidiaries, or any person who would be covered by Item 404(a) of Regulation
S-K or any corporation or other entity controlled by such officer, employee,
consultant, director or person.

               (u) Securities Act of 1933. The Company has complied in all
material respects with all applicable federal and state securities laws in
connection with the offer, issuance and sale of the Shares hereunder.

                                        8
<PAGE>   10

                  (i) Each Prospectus included as part of the Registration
Statement as originally filed or as part of any amendment or supplement thereto,
or filed pursuant to Rule 424 under the Securities Act, complied when so filed
in all material respects with the provisions of the Securities Act. The
Commission has not issued any order preventing or suspending the use of any
Prospectus.

                  (ii) The Company meets the requirements for the use of Form
S-3 under the Securities Act. The Registration Statement in the form in which it
became effective and also in such form as it may be when any post-effective
amendment thereto became effective and the Prospectus and any supplement or
amendment thereto when filed with the Commission under Rule 424(b) under the
Securities Act, complied in all material respects with the provisions of the
Securities Act and did not at any such times contain an untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein (in the case of the Prospectus, in the
light of the circumstances under which they made) not misleading, except that
this representation and warranty does not apply to statements in or omissions
from the Registration Statement or the Prospectus made in reliance upon and in
conformity with information relating to the Purchaser furnished to the Company
in writing by or on behalf of the Purchaser through you expressly for use
therein.

                  (iii) The Company has not distributed and, prior to the
completion of the distribution of the Shares, will not distribute any offering
material in connection with the offering and sale of the Shares other than the
Registration Statement, the Prospectus or other materials, if any, permitted by
the Securities Act.

               (v) Employees. As of the date hereof, neither the Company nor any
subsidiary has any collective bargaining arrangements or agreements covering any
of its employees, except as set forth in the Commission Documents or the
Commission Filings or on Schedule 3.1(v) attached hereto. As of the date hereof,
except as set forth in the Commission Documents or the Commission Filings or on
Schedule 3.1(v) attached hereto, neither the Company nor any subsidiary has any
employment contract, agreement regarding proprietary information, noncompetition
agreement, nonsolicitation agreement, confidentiality agreement, or any other
similar contract or restrictive covenant, relating to the right of any officer,
employee or consultant to be employed or engaged by the Company or such
subsidiary. As of the date hereof, since December 31, 1998, except as disclosed
in the Registration Statement, the Commission Documents, the Commission Filings
or Schedule 3.1(v), no officer, consultant or key employee of the Company or any
subsidiary whose termination, either individually or in the aggregate, could
reasonably be expected to have a Material Adverse Effect, has terminated or, to
the knowledge of the Company, has any present intention of terminating his or
her employment or engagement with the Company or any subsidiary.

               (w) Use of Proceeds. The proceeds from the sale of the Shares
will be used by the Company and its subsidiaries for general corporate purposes.

               (x) Public Utility Holding Company Act and Investment Company Act
Status. The Company is not a "holding company" or a "public utility company" as
such terms are defined in the Public Utility Holding Company Act of 1935, as
amended. The Company is not, and as a result of and immediately upon Closing
will not be, an "investment company" or a

                                        9
<PAGE>   11

company "controlled" by an "investment company," within the meaning of the
Investment Company Act of 1940, as amended.

               (y) ERISA. No liability to the Pension Benefit Guaranty
Corporation has been incurred with respect to any Plan by the Company or any of
its subsidiaries which is or would have a Material Adverse Effect. The execution
and delivery of this Agreement and the issue and sale of the Shares will not
involve any transaction which is subject to the prohibitions of Section 406 of
ERISA or in connection with which a tax could be imposed pursuant to Section
4975 of the Internal Revenue Code of 1986, as amended, provided that, if any of
the Purchaser, or any person or entity that owns a beneficial interest in any of
the Purchaser, is an "employee pension benefit plan" (within the meaning of
Section 3(2) of ERISA) with respect to which the Company is a "party in
interest" (within the meaning of Section 3(14) of ERISA), the requirements of
Sections 407(d)(5) and 408(e) of ERISA, if applicable, are met. As used in this
Section 2.1(ac), the term "Plan" shall mean an "employee pension benefit plan"
(as defined in Section 3 of ERISA) which is or has been established or
maintained, or to which contributions are or have been made, by the Company or
any subsidiary or by any trade or business, whether or not incorporated, which,
together with the Company or any subsidiary, is under common control, as
described in Section 414(b) or (c) of the Code.

               (z) Acknowledgment Regarding Purchaser's Purchase of Shares. The
Company acknowledges and agrees that the Purchaser is acting solely in the
capacity of arm's length purchaser with respect to this Agreement and the
transactions contemplated hereunder. The Company further acknowledges that the
Purchaser is not acting as a financial advisor or fiduciary of the Company (or
in any similar capacity) with respect to this Agreement and the transactions
contemplated hereunder and any advice given by the Purchaser or any of its
representatives or agents in connection with this Agreement and the transactions
contemplated hereunder is merely incidental to the Purchaser's purchase of the
Shares.

        SECTION 3.2 Representation and Warranties of the Purchaser. The
Purchaser hereby makes the following representations and warranties to the
Company:

               (a) Organization and Standing of the Purchaser. The Purchaser is
a limited liability company duly organized, validly existing and in good
standing under the laws of the Commonwealth of the Bahamas.

               (b) Authorization and Power. The Purchaser has the requisite
corporate power and authority to enter into and perform this Agreement and to
purchase the Shares in accordance with the terms hereof. The execution, delivery
and performance of this Agreement by Purchaser and the consummation by it of the
transactions contemplated hereby have been duly authorized by all necessary
corporate action, and no further consent or authorization of the Purchaser, its
Board of Directors or stockholders is required. This Agreement constitutes, or
shall constitute when executed and delivered, a valid and binding obligation of
the Purchaser enforceable against the Purchaser in accordance with its terms,
except as such enforceability may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium, liquidation, conservatorship,
receivership, or similar laws relating to, or affecting generally the
enforcement of, creditor's rights and remedies or by other equitable principles
of general application.

                                       10
<PAGE>   12

               (c) No Conflicts. The execution, delivery and performance of this
Agreement and the consummation by the Purchaser of the transactions contemplated
hereby and thereby or relating hereto do not and will not (i) result in a
violation of such Purchaser's charter documents or bylaws or (ii) conflict with,
or constitute a default (or an event which with notice or lapse of time or both
would become a default) under, or give to others any rights of termination,
amendment, acceleration or cancellation of any material agreement, mortgage,
deed of trust, indenture, note, bond, license, lease agreement, instrument or
obligation to which the Purchaser is a party, (iii) create or impose or lien,
charge or encumbrance on any property of the Purchaser under any agreement or
any commitment to which the Purchaser is party or by which the Purchaser is on
or by which any of its respective properties or assets are bound or (iv) result
in a violation of any law, rule, or regulation, or any order, judgment or decree
of any court or governmental agency applicable to the Purchaser or its
properties, except for such conflicts, defaults and violations as would not,
individually or in the aggregate, prohibit or otherwise interfere with the
ability of the Purchaser to enter into and perform its obligations under this
Agreement in any material respect. The Purchaser is not required to obtain any
consent, authorization or order of, or make any filing or registration with, any
court or governmental agency in order for it to execute, deliver or perform any
of its obligations under this Agreement or to purchase the Shares in accordance
with the terms hereof, provided that for purposes of the representation made in
this sentence, the Purchaser is assuming and relying upon the accuracy of the
relevant representations and agreements of the Company herein.

               (d) Information. The Purchaser and its advisors, if any, have
been furnished with all materials relating to the business, finances and
operations of the Company and materials relating to the offer and sale of the
Shares which have been requested by the Purchaser. The Purchaser and its
advisors, if any, have been afforded the opportunity to ask questions of the
Company. The Purchaser has sought such accounting, legal and tax advice as it
has considered necessary to make an informed investment decision with respect to
its acquisition of the Shares. Purchaser understands that it (and not the
Company) shall be responsible for its own tax liabilities that may arise as a
result of this investment or the transactions contemplated by this Agreement.

                                    ARTICLE 4

                                    COVENANTS

        The Company covenants with the Purchaser as follows, which covenants are
for the benefit of the Purchaser and its permitted assignees (as defined
herein).

        SECTION 4.1 Securities. The Company shall notify the Commission and
NASD, if applicable, in accordance with their rules and regulations, of the
transactions contemplated by this Agreement, and shall take all other necessary
action and proceedings as may be required and permitted by applicable law, rule
and regulation, for the legal and valid issuance of the Shares to the Purchaser
or subsequent holders.

        SECTION 4.2 Registration and Listing. The Company will take all action
necessary to cause its Common Stock to continue to be registered under Sections
12(b) or 12(g) of the Exchange Act, will comply in all respects with its
reporting and filing obligations under the Exchange Act, and will not take any
action or file any document (whether or not permitted by the

                                       11
<PAGE>   13

Securities Act or the rules promulgated thereunder) to terminate or suspend such
registration or to terminate or suspend its reporting and filing obligations
under the Exchange Act or Securities Act, except as permitted herein. The
Company will take all action necessary to continue the listing or trading of its
Common Stock and the listing of the Shares purchased by Purchaser hereunder on
the NASDAQ or any relevant market or system, if applicable, and will comply in
all respects with the Company's reporting, filing and other obligations under
the bylaws or rules of the NASD or any relevant market or system.

        SECTION 4.3 Registration Statement. Before the Purchaser shall be
obligated to accept a Draw Down request from the Company, the Company shall have
caused a sufficient number of shares of Common Stock to be registered to cover
the Shares to be issued in connection with this Agreement.

        SECTION 4.4 Compliance with Laws.

               (a) The Company shall comply, and cause each subsidiary to
comply, with all applicable laws, rules, regulations and orders, noncompliance
with which could have a Material Adverse Effect.

               (b) The Company will not be obligated to issue and the Purchaser
will not be obligated to purchase any shares of the Company's Common Stock which
would result in the issuance under this Agreement of more than nineteen and
nine-tenths percent (19.9%) of the issued and outstanding shares of the
Company's Common Stock.

        SECTION 4.5 Keeping of Records and Books of Account. The Company shall
keep and cause each subsidiary to keep adequate records and books of account, in
which complete entries will be made in accordance with GAAP consistently
applied, reflecting all financial transactions of the Company and its
subsidiaries, and in which, for each fiscal year, all proper reserves for
depreciation, depletion, obsolescence, amortization, taxes, bad debts and other
purposes in connection with its business shall be made.

        SECTION 4.6 Reporting Requirements. Upon request, the Company shall
furnish the following to the Purchaser so long as such Purchaser shall be
obligated hereunder to purchase Shares:

               (a) Quarterly Reports filed with the Commission on Form 10-Q as
soon as available, and in any event within 45 days after the end of each of the
first three fiscal quarters of the Company; and

               (b) Annual Reports filed with the Commission on Form 10-K as soon
as available, and in any event within 90 days after the end of each fiscal year
of the Company.

        SECTION 4.7 [Intentionally Omitted.]

        SECTION 4.8 Effective Registration Statement. If, at the time this
Agreement is executed and delivered, it is necessary for the Registration
Statement or a post-effective amendment thereto to be declared effective before
the offering of the Shares may commence, the Company will endeavor to cause the
Registration Statement or such post-effective amendment to become effective as
soon as reasonably practicable and will advise you promptly and, if

                                       12
<PAGE>   14

requested by the Purchaser, will confirm such advice in writing, when it
receives notice that the Registration Statement or such post-effective amendment
has become effective.

        SECTION 4.9 No Stop Orders. The Company will advise the Purchaser
promptly and, if requested by the Purchaser, will confirm such advice in
writing: (i) of its receipt of notice of any request by the Commission for
amendment of or a supplement to the Registration Statement, any Prospectus or
for additional information; (ii) of its receipt of notice of the issuance by the
Commission of any stop order suspending the effectiveness of the Registration
Statement or of the suspension of qualification of the Shares for offering or
sale in any jurisdiction or the initiation of any proceeding for such purpose;
and (iii) of its becoming aware of the happening of any event, which makes any
statement of a material fact made in the Registration Statement or the
Prospectus (as then amended or supplemented) untrue or which requires the making
of any additions to or changes in the Registration Statement or the Prospectus
(as then amended or supplemented) in order to state a material fact required by
the Securities Act or the regulations thereunder to be stated therein or
necessary in order to make the statements therein not misleading, or of the
necessity to amend or supplement the Prospectus (as then amended or
supplemented) to comply with the Securities Act or any other law. If at any time
the Commission shall issue any stop order suspending the effectiveness of the
Registration Statement, the Company will make commercially reasonable efforts to
obtain the withdrawal of such order at the earliest possible time.

        SECTION 4.10 Amendments to the Registration Statement. The Company will
not (i) file any amendment to the Registration Statement or make any amendment
or supplement to the Prospectus of which the Purchaser shall not previously have
been advised or to which the Purchaser shall reasonably object after being so
advised or (ii) so long as, in the reasonable opinion of counsel for the
Purchaser, a Prospectus is required to be delivered in connection with sales by
any Purchaser or dealer, file any information, documents or reports pursuant to
the Exchange Act without delivering a copy of such information, documents or
reports to the Purchaser, promptly following such filing.

        SECTION 4.11 No Stop Orders. Prior to the execution and delivery of this
Agreement, the Company will deliver to the Purchaser, without charge, in such
quantities as reasonably requested by the Purchaser, copies of each form of
Prospectus. As soon after the execution and delivery of this Agreement as
possible and thereafter from time to time for such period as in the opinion of
counsel for the Purchasers a prospectus is required by the Securities Act to be
delivered in connection with sales by the Purchaser, the Company will
expeditiously deliver to the Purchaser, without charge, as many copies of the
Prospectus (and of any amendment or supplement thereto) as the Purchaser may
reasonably request. The Company consents to the use of the Prospectus (and of
any amendment or supplement thereto) in accordance with the provisions of the
Securities Act and with the securities or Blue Sky laws of the jurisdictions in
which the Shares may be sold by the Purchaser, in connection with the offering
and sale of the Shares and for such period of time thereafter as the Prospectus
is required by the Securities Act to be delivered in connection with sales of
the Shares. If during such period of time any event shall occur that in the
judgment of the Company or in the opinion of counsel for the Purchaser is
required to be set forth in the Prospectus (as then amended or supplemented) or
should be set forth therein in order to make the statements therein, in the
light of the circumstances under which they were made, not misleading, or if it
is necessary to supplement or amend the Prospectus to comply with the Securities
Act or any other law, the Company will forthwith

                                       13
<PAGE>   15

prepare and, subject to the provisions of Section 4.10 above, file with the
Commission an appropriate supplement or amendment thereto, and will
expeditiously furnish to the Purchaser a reasonable number of copies thereof.

                                    ARTICLE 5

                      CONDITIONS TO CLOSING AND DRAW DOWNS

        SECTION 5.1 Conditions Precedent to the Obligation of the Company to
Sell the Shares. The obligation hereunder of the Company to issue and sell the
Shares to the Purchaser is subject to the satisfaction or waiver, at or before
each Draw Down, of each of the conditions set forth below. These conditions are
for the Company's sole benefit and may be waived by the Company at any time in
its sole discretion.

               (a) Accuracy of the Purchaser's Representations and Warranties.
The representations and warranties of the Purchaser shall be true and correct in
all material respects as of the date when made and as of each Draw Down request
as though made at that time, except for representations and warranties that are
expressly made as of a particular date.

               (b) Effective Registration Statement. The Registration Statement
registering the Shares shall have been declared effective by the Commission and
shall have been amended or supplemented, as required, to disclose the sale of
the Shares prior to each Settlement Date, as applicable.

               (c) Performance by the Purchaser. The Purchaser shall have
performed, satisfied and complied in all material respects with all covenants,
agreements and conditions required by this Agreement to be performed, satisfied
or complied with by the Purchaser at or prior to each Settlement Date.

               (d) No Injunction. No statute, regulation, executive order,
decree, ruling or injunction shall have been enacted, entered, promulgated or
endorsed by any court or governmental authority of competent jurisdiction which
prohibits the consummation of any of the transactions contemplated by this
Agreement.

               (e) No Suspension, Etc. Trading in the Company's Common Stock
shall not have been suspended by the Commission or the NASD (except for any
suspension of trading of limited duration agreed to by the Company, which
suspension shall be terminated prior to Closing), and, at any time prior to each
Draw Down request, trading in securities generally as reported on NASDAQ shall
not have been suspended or limited, or minimum prices shall not have been
established on securities whose trades are reported by American Stock Exchange,
or on the New York Stock Exchange, nor shall a banking moratorium have been
declared either by the United States or New York State authorities, nor shall
there have occurred any material outbreak or escalation of hostilities or other
national or international calamity or crisis of such magnitude in its effect on,
or any material adverse change in any financial market which, in each case, in
the judgment of the Company, makes it impracticable or inadvisable to issue the
Shares.

               (f) No Proceedings or Litigation. No action, suit or proceeding
before any arbitrator or any governmental authority shall have been commenced,
and no investigation by any governmental authority shall have been threatened,
against the Company or any subsidiary,

                                       14
<PAGE>   16

or any of the officers, directors or affiliates of the Company or any subsidiary
seeking to restrain, prevent or change the transactions contemplated by this
Agreement, or seeking damages in connection with such transactions.

        SECTION 5.2 Conditions Precedent to the Obligation of the Purchaser to
Close. The obligation hereunder of the Purchaser to enter this Agreement is
subject to the satisfaction or waiver, at or before the Closing, of each of the
conditions set forth below. These conditions are for the Purchaser's sole
benefit and may be waived by the Purchaser at any time in its sole discretion.

               (a) Effective Registration Statement. The Registration Statement
registering the Shares shall have been declared effective by the Commission and
shall have been amended or supplemented, as required, to disclose the sale of
the Shares prior to the Closing Date or each Settlement Date, as applicable.

               (b) Performance by the Company. The Company shall have performed,
satisfied and complied in all material respects with all covenants, agreements
and conditions required by this Agreement to be performed, satisfied or complied
with by the Company at or prior to the Closing.

               (c) No Suspension, Etc. Trading in the Company's Common Stock
shall not have been suspended by the Commission or the NASD (except for any
suspension of trading of limited duration agreed to by the Company, which
suspension shall be terminated prior to Closing), and, at any time prior to the
Closing, trading in securities generally as reported on NASDAQ shall not have
been suspended or limited, or minimum prices shall not have been established on
securities whose trades are reported by the American Stock Exchange, or on the
New York Stock Exchange, nor shall a banking moratorium have been declared
either by the United States or New York State authorities, nor shall there have
occurred any material outbreak or escalation of hostilities or other national or
international calamity or crisis of such magnitude in its effect on, or any
material adverse change in any financial market which, in each case, in the
judgment of the Purchaser, makes it impracticable or inadvisable to purchase the
Shares.

               (d) No Injunction. No statute, rule, regulation, executive order,
decree, ruling or injunction shall have been enacted, entered, promulgated or
endorsed by any court or governmental authority of competent jurisdiction which
prohibits the consummation of any of the transactions contemplated by this
Agreement.

               (e) No Proceedings or Litigation. No action, suit or proceeding
before any arbitrator or any governmental authority shall have been commenced,
and no investigation by any governmental authority shall have been threatened,
against the Company or any subsidiary, or any of the officers, directors or
affiliates of the Company or any subsidiary seeking to restrain, prevent or
change the transactions contemplated by this Agreement, or seeking damages in
connection with such transactions.

               (f) Opinion of Counsel, Etc. At the Closing, the Purchaser shall
have received an opinion of counsel to the Company, dated the date of Closing,
in the form of Exhibit A hereto, and such other certificates and documents as
the Purchaser or its counsel shall reasonably require incident to the Closing.

                                       15
<PAGE>   17

        SECTION 5.3 Conditions Precedent to the Obligation of the Purchaser to
Accept a Draw Down and Purchase the Shares. The obligation hereunder of the
Purchaser to accept a Draw Down request and to acquire and pay for the Shares is
subject to the satisfaction or waiver, at or before each Draw Down Exercise
Date, of each of the conditions set forth below. The conditions are for the
Purchaser's sole benefit and may be waived by the Purchaser at any time in its
sole discretion.

               (a) Accuracy of the Company's Representations and Warranties.
Each of the representations and warranties of the Company shall be true and
correct in all material respects as of the date when made and as of the Draw
Down Exercise Date as though made at that time (except for representations and
warranties that speak as of a particular date).

               (b) Effective Registration Statement. The Registration Statement
registering the Shares shall have been declared effective by the Commission and
shall have been amended or supplemented, as required, to disclose the sale of
the Shares prior to the Closing Date or each Settlement Date, as applicable.

               (c) No Suspension. Trading in the Company's Common Stock shall
not have been suspended by the Commission or the NASD (except for any suspension
of trading of limited duration agreed to by the Company, which suspension shall
be terminated prior to each Draw Down request), and, at any time prior to such
request, trading in securities generally as reported by the American Stock
Exchange shall not have been suspended or limited, or minimum prices shall not
have been established on securities whose trades are reported by the American
Stock Exchange.

               (d) Material Adverse Effect; Material Change in Ownership. No
Material Adverse Effect and no Material Change in Ownership shall have occurred.

                                    ARTICLE 6

                                 DRAW DOWN TERMS

        SECTION 6.1 Drawn Down Terms. Subject to the satisfaction of the
conditions set forth in this Agreement, the parties agree as follows:

               (a) The Company, may, in its sole discretion, issue and exercise
a draw down of up to $4,000,000 (a "Draw Down") during each Draw Down Pricing
Period, which Draw Down the Purchaser will be obligated to accept. Prior to
issuing any Draw Down request, the Company shall have at least $4,000,000
registered under the Registration Statement.

               (b) The number of Shares to be issued in connection with each
Draw Down shall be equal to the sum of the quotients (for each trading day of
the Draw Down Pricing Period for which the VWAP equals or exceeds the Threshold
Price) of (x) 1/18th of the Draw Down Amount divided by (y) the applicable Draw
Down Discount Price.

               (c) Only one Draw Down shall be allowed in each Draw Down Pricing
Period.

                                       16
<PAGE>   18

               (d) The number of Shares purchased by the Purchaser with respect
to each Draw Down shall be determined on a daily basis during each Draw Down
Pricing Period and settled on a monthly basis (the "Settlement Date").

               (e) There shall be a minimum of five (5) trading days between
Draw Downs.

               (f) There shall be a maximum of twelve (12) monthly Draw Downs
during the term of this Agreement.

               (g) At the end of each Draw Down Pricing Period, the Purchaser's
total Draw Down commitment shall be reduced by $4,000,000 regardless of the Draw
Down Amount requested by the Company.

               (h) Each Draw Down will expire on the last trading day of each
Draw Down Pricing Period.

               (i) If the VWAP on a given trading day is less than the Threshold
Price, then the total amount of the Draw Down will be reduced by 1/18th and no
Shares will be purchased or sold with respect to such trading day.
Notwithstanding anything in the foregoing to the contrary, if the VWAP on a
given trading day is less than the Threshold Price, the Purchaser may elect in
its sole discretion to purchase Shares at the Threshold Price and shall take
into account a discount of 92% of the VWAP. At no time shall the Threshold Price
be set below $10.00 unless agreed upon by the Company and the Purchaser. If
trading in the Company's Common Stock is suspended for any reason for more than
three (3) hours in any trading day, at the Purchaser's option, the price of the
Common Stock shall be deemed to be below the Threshold Price for that trading
day.

               (j) The Company must inform the Purchaser via facsimile
transmission as to the Draw Down Amount the Company wishes to exercise before
commencement of trading on the first trading day of the Draw Down Pricing Period
(the "Draw Down Notice"). In addition to the Draw Down Amount, the Company shall
set the Threshold Price with each Draw Down Notice and shall designate the first
trading day of the Draw Down Pricing Period. At no time shall the Purchaser be
required to purchase more than $4,000,000 of the Company's Common Stock for a
given Draw Down Pricing Period so that if the Company chooses not to exercise
the Draw Down in a given Draw Down Pricing Period the Purchaser is not obligated
to purchase more than $4,000,000 in a subsequent Draw Down Pricing Period.

               (k) On each Settlement Date, the Company shall deliver the Shares
purchased by the Purchaser to the Purchaser or to The Depositary Trust Company
("DTC") on the Purchaser's behalf via DWAC. The Company shall cause such Shares
to be credited to the DTC account designated by the Purchaser upon receipt by
the Company of payment for the Draw Down into an account designated by the
Company; provided that the Shares are received by the Purchaser no later than
1:00 p.m. EST. The delivery of the shares of Common Stock into the Purchaser's
DTC account in exchange for payment therefor shall be referred to herein as
"Settlement". The Purchaser shall coordinate Settlement with the Company through
DTC.

               (l) If during any Draw Down Pricing Period, the Company shall
issue any shares of Common Stock (other than shares of Common Stock issued to
corporate partners or in connection with a joint venture), the purchaser may in
its sole discretion (i) purchase $4,000,000

                                       17
<PAGE>   19

of shares of Common Stock at the price at which the Company issued shares of
Common Stock during such Draw Down Pricing Period, (ii) purchase $4,000,000 of
shares of Common Stock at the applicable Draw Down Discount Price, or (iii)
elect not to purchase any Shares during such Draw Down Pricing Period.

                                    ARTICLE 7

                                   TERMINATION

        SECTION 7.1 Termination by Mutual Consent. The term of this Agreement
shall be thirteen (13) months from the Effective Date. This Agreement may be
terminated at any time by mutual consent of the parties.

        SECTION 7.2 Other Termination. The Purchaser may terminate this
Agreement upon (x) one (1) day's notice if the Company issues convertible
debentures or enters an equity financing facility as set forth in Section 4.7
without the Purchaser's prior written consent, or (y) one (1) day's notice if an
event resulting in a Material Adverse Effect or a Material Change of Control in
Ownership has occurred.

        SECTION 7.3 Effect of Termination. In the event of termination by the
Company or the Purchaser, written notice thereof shall forthwith be given to the
other party and the transactions contemplated by this Agreement shall be
terminated without further action by either party. If this Agreement is
terminated as provided in Section 7.1 or 7.2 herein, this Agreement shall become
void and of no further force and effect, except as provided in Section 9.10.
Nothing in this Section 7.3 shall be deemed to release the Company or the
Purchaser from any liability for any breach under this Agreement, or to impair
the rights of the Company and the Purchaser to compel specific performance by
the other party of its obligations under this Agreement.

                                    ARTICLE 8

                                 INDEMNIFICATION

        SECTION 8.1 General Indemnity.

               (a) Indemnification by the Company. The Company will indemnify
and hold harmless the Purchaser and each person, if any, who controls the
Purchaser within the meaning of Section 15 of the Securities Act or Section
20(a) of the Exchange Act from and against any losses, claims, damages,
liabilities and expenses (including reasonable costs of defense and
investigation and all attorney's fees) to which the Purchaser and each person,
if any, who controls the Purchaser may become subject, under the Securities Act
or otherwise, insofar as such losses, claims, damages, liabilities and expenses
(or actions in respect thereof) arise out of or are based upon, (i) any untrue
statement or alleged untrue statement of a material fact contained, or
incorporated by reference, in the Registration Statement relating to Common
Stock being sold to the Purchaser (including the any prospectus supplement filed
in connection with the transactions contemplated hereunder (the "Prospectus
Supplement") which are a part of it), or any amendment or supplement to it, or
(ii) the omission or alleged omission to state in that Registration Statement or
any document incorporated by reference in the Registration Statement, a material
fact required to be stated therein or necessary to make the statements therein
not misleading.

                                       18
<PAGE>   20

        The Company will reimburse the Purchaser and each such controlling
person promptly upon demand for any legal or other costs or expenses reasonably
incurred by or the controlling person in investigating, defending against, or
preparing to defend against any such claim, action, suit or proceeding, except
that the Company will not be liable to the extent a claim or action which
results in a loss, claim, damage, liability or expense arises out of, or is
based upon, an untrue statement, alleged untrue statement, omission or alleged
omission, included in any Prospectus or Prospectus Supplement or any amendment
or supplement to the Prospectus or Prospectus Supplement in reliance upon, and
in conformity with, written information furnished by the Purchase to the Company
for inclusion in the Prospectus or Prospectus Supplement.

               (b) Indemnification by the Purchaser. The Purchaser will
indemnify and hold harmless the Company, each of its directors and officers, and
each person, if any, who controls the Company within the meaning of Section 15
of the Securities Act or Section 20(a) of the Exchange Act from and against any
expenses (including reasonable costs of defense and investigation and all
attorneys fees) to which the Purchaser and each person, if any, who controls the
Purchaser may become subject, under the Securities Act or otherwise, insofar as
such losses, claims, damages, liabilities and expenses (or actions in respect
thereof) arise out of or are based upon, (i) any untrue statement or alleged
untrue statement of a material fact contained in any Prospectus or Prospectus
Supplement or any amendment or supplement to it or (ii) the omission or alleged
omission to state in any Prospectus or Prospectus Supplement or any amendment or
supplement to it a material fact required to be stated therein or necessary to
make the statements therein not misleading, to the extent, but only to the
extent, the untrue statement, alleged untrue statement, omission or alleged
omission was made in reliance upon, and in conformity with, written information
furnished by the Purchaser to the Company for inclusion in the Prospectus or
Prospectus Supplement or an amendment or supplement to it, and the Purchaser
will reimburse the Company and each such director, officer or controlling person
promptly upon demand for any legal or other costs or expenses reasonably
incurred by the Company or the other person in investigating, defending against,
or preparing to defend against any such claim, action, suit or proceeding.

        SECTION 8.2 Indemnification Procedures. Promptly after a person receives
notice of a claim or the commencement of an action for which the person intends
to seek indemnification under paragraph (a) or (b) of Section 8.1, the person
will notify the indemnifying party in writing of the claim or commencement of
the action, suit or proceeding, but failure to notify the indemnifying party
will not relieve the indemnifying party from liability under paragraph (a) or
(b) of Section 8.1, except to the extent it has been materially prejudiced by
the failure to give notice. The indemnifying party will be entitled to
participate in the defense of any claim, action, suit or proceeding as to which
indemnification is being sought, and if the indemnifying party acknowledges in
writing the obligation to indemnify the party against whom the claim or action
is brought, the indemnifying party may (but will not be required to) assume the
defense against the claim, action, suit or proceeding with counsel satisfactory
to it. After an indemnifying party notifies an indemnified party that the
indemnifying party wishes to assume the defense of a claim, action, suit or
proceeding the indemnifying party will not be liable for any legal or other
expenses incurred by the indemnified party in connection with the defense
against the claim, action, suit or proceeding except that if, in the opinion of
counsel to the indemnifying party, one or more of the indemnified parties should
be separately represented in connection with a claim, action, suit or proceeding
the indemnifying party will pay the reasonable fees and expenses of one separate
counsel for the indemnified parties. Each indemnified party, as a condition to

                                       19
<PAGE>   21

receiving indemnification as provided in Paragraph (a) or (b) or Section 8.1,
will cooperate in all reasonable respects with the indemnifying party in the
defense of any action or claim as to which indemnification is sought. No
indemnifying party will be liable for any settlement of any action effected
without its prior written consent. No indemnifying party will, without the prior
written consent of the indemnified party, effect any settlement of a pending or
threatened action with respect which an indemnified party is, or is informed
that it may be, made a party and for which it would be entitled to
indemnification, unless the settlement includes an unconditional release of the
indemnified party from all liability and claims which are the subject matter of
the pending or threatened action.

        If for any reason the indemnification provided for in this Agreement is
not available to, or is not sufficient to hold harmless, an indemnified party in
respect of any loss or liability referred to in paragraph (a) or (b) of Section
8.1, each indemnifying party will, in lieu of indemnifying the indemnified
party, contribute to the amount paid or payable by the indemnified party,
contribute to the amount paid or payable by the indemnified party as a result of
the loss or liability, (i) in the proportion which is appropriate to reflect the
relative benefits received by the indemnifying party on the one hand and by the
indemnified party on the other from the sale of stock which is the subject of
the claim, action, suit or proceeding which resulted in the loss or liability or
(ii) if that allocation is not permitted by applicable law, in such proportion
as is appropriate to reflect not only the relative benefits of the sale of
stock, but also the relative fault of the indemnifying party and the indemnified
party with respect to the statements or omissions which are the subject of the
claim, action, suit or proceeding that resulted in the loss or liability, as
well as any other relevant equitable considerations.

                                    ARTICLE 9

                                  MISCELLANEOUS

        SECTION 9.1 Fees and Expenses. The Company shall pay all reasonable fees
and expenses related to the transactions contemplated by this Agreement;
provided, that the Company shall pay, at the Closing, all reasonable attorneys
fees and expenses (exclusive of disbursements and out-of-pocket expenses)
incurred by the Purchaser up to $35,000 in connection with the preparation,
negotiation, execution and delivery of this Agreement. In addition, the Company
shall pay all reasonable fees and expenses incurred by the Purchaser in
connection with any amendments, modifications or waivers of this Agreement or
incurred in connection with the enforcement of this Agreement, including,
without limitation, all reasonable attorneys fees and expenses. The Company
shall pay all stamp or other similar taxes and duties levied in connection with
issuance of the Shares pursuant hereto.

        SECTION 9.2 Specific Enforcement, Consent to Jurisdiction.

               (a) The Company and the Purchaser acknowledge and agree that
irreparable damage would occur in the event that any of the provisions of this
Agreement were not performed in accordance with their specific terms or were
otherwise breached. It is accordingly agreed that the parties shall be entitled
to an injunction or injunctions to prevent or cure breaches of the provisions of
this Agreement and to enforce specifically the terms and provisions hereof or
thereof, this being in addition to any other remedy to which any of them may be
entitled by law or equity.

                                       20
<PAGE>   22

               (b) Each of the Company and the Purchaser (i) hereby irrevocably
submits to the jurisdiction of the United States District Court and other courts
of the United States sitting in the State of Delaware for the purposes of any
suit, action or proceeding arising out of or relating to this Agreement and (ii)
hereby waives, and agrees not to assert in any such suit, action or proceeding,
any claim that it is not personally subject to the jurisdiction of such court,
that the suit, action or proceeding is brought in an inconvenient forum or that
the venue of the suit, action or proceeding is improper. Each of the Company and
the Purchaser consents to process being served in any such suit, action or
proceeding by mailing a copy thereof to such party at the address in effect for
notices to it under this Agreement and agrees that such service shall constitute
good and sufficient service of process and notice thereof. Nothing in this
Section shall affect or limit any right to serve process in any other manner
permitted by law.

        SECTION 9.3 Entire Agreement; Amendment. This Agreement contains the
entire understanding of the parties with respect to the matters covered hereby
and, except as specifically set forth herein, neither the Company nor the
Purchaser makes any representations, warranty, covenant or undertaking with
respect to such matters. No provision of this Agreement may be waived or amended
other than by a written instrument signed by the party against whom enforcement
of any such amendment or waiver is sought.

        SECTION 9.4 Notices. Any notice, demand, request, waiver or other
communication required or permitted to be given hereunder shall be in writing
and shall be effective (a) upon hand delivery, by telex (with correct answer
back received), telecopy or facsimile at the address or number designated below
(if delivered on a business day during normal business hours where such notice
is to be received), or the first business day following such delivery (if
delivered other than on a business day during normal business hours where such
notice is to be received) or (b) on the second business day following the date
of mailing by express courier service, fully prepaid, addressed to such address,
or upon actual receipt of such mailing, whichever shall first occur. The
addresses for such communications shall be:

If to the Company:    Aviron
                      297 North Bernado Avenue
                      Mountain View, CA  94043
                      (650) 919-6500
                      (650) 919-6610
                      Attention:  Fred Kurland
                             Chief Financial Officer

With copies to:       Cooley Godward LLP
                      3000 El Camino Real
                      5 Palo Alto Square
                      Palo Alto, CA 94306
                      Telephone Number: (650) 843-5000
                      Fax:  (650) 857-0663
                      Attention:  Robert Brigham

If to the Purchaser:  Acqua Wellington North American
                      Equities Fund, Ltd.
                      c/o Mees Pierson Fund Services (Bahamas) Ltd.

                                       21
<PAGE>   23

                      Montague Sterling Centre
                      East Bay Street, P. O. Box SS-6238
                      Nassau, Bahamas

        Any party hereto may from time to time change its address for notices by
giving at least ten (10) days written notice of such changed address to the
other party hereto.

        SECTION 9.5 Waivers. No waiver by either party of any default with
respect to any provision, condition or requirement of this Agreement shall be
deemed to be a continuing waiver in the future or a waiver of any other
provisions, condition or requirement hereof, nor shall any delay or omission of
any party to exercise any right hereunder in any manner impair the exercise of
any such right accruing to it thereafter.

        SECTION 9.6 Headings. The article, section and subsection headings in
this Agreement are for convenience only and shall not constitute a part of this
Agreement for any other purpose and shall not be deemed to limit or affect any
of the provisions hereof.

        SECTION 9.7 Successors and Assigns. The Purchaser may not assign this
Agreement to any person without the prior consent of the Company, which consent
will not be unreasonably withheld. This Agreement shall be binding upon and
inure to the benefit of the parties and their successors and assigns. The
parties hereto may not amend this Agreement or any rights or obligations
hereunder without the prior written consent of the Company and each Purchaser to
be affected by the amendment. After Closing, the assignment by a party to this
Agreement of any rights hereunder shall not affect the obligations of such party
under this Agreement.

        SECTION 9.8 Governing Law. This Agreement shall be governed by and
construed in accordance with the internal laws of the State of Delaware, without
giving effect to the choice of law provisions.

        SECTION 9.9 Survival. The representations and warranties of the Company
and the Purchaser contained in Article III and the covenants contained in
Article IV shall survive the execution and delivery hereof and the Closing until
the termination of this Agreement, and the agreements and covenants set forth in
Article VIII of this Agreement shall survive the execution and delivery hereof
and the Closing hereunder.

        SECTION 9.10 Counterparts. This Agreement may be executed in any number
of counterparts, all of which taken together shall constitute one and the same
instrument and shall become effective when counterparts have been signed by each
party and delivered to the other parties hereto, it being understood that all
parties need not sign the same counterpart. In the event any signature is
delivered by facsimile transmission, the party using such means of delivery
shall cause four additional executed signature pages to be physically delivered
to the other parties within five days of the execution and delivery hereof.

        SECTION 9.11 Publicity. Prior to the Closing, neither the Company nor
the Purchaser shall issue any press release or otherwise make any public
statement or announcement with respect to this Agreement or the transactions
contemplated hereby or the existence of this Agreement. In the event the Company
is required by law, based upon an opinion of the Company's counsel, that the
Company must issue a press release or otherwise make a public

                                       22
<PAGE>   24

statement or announcement with respect to this Agreement prior to the Closing,
the Company shall consult with the Purchaser on the form and substance of such
press release. After the Closing, the Company may issue a press release or
otherwise make a public statement or announcement with respect to this Agreement
or the transactions contemplated hereby or the existence of this Agreement;
provided, that prior to issuing any such press release, making any such public
statement or announcement, the Company obtains the prior consent of the
Purchaser, which consent shall not be unreasonably withheld or delayed.

        SECTION 9.12 Severability. The provisions of this Agreement are
severable and, in the event that any court of competent jurisdiction shall
determine that any one or more of the provisions or part of the provisions
contained in this Agreement shall, for any reason, be held to be invalid,
illegal or unenforceable in any respect, such invalidity, illegality or
unenforceability shall not affect any other provision or part of a provision of
this Agreement, and this Agreement shall be reformed and construed as if such
invalid or illegal or unenforceable provision, or part of such provision, had
never been contained herein, so that such provisions would be valid, legal and
enforceable to the maximum extent possible.

        SECTION 9.13 Further Assurances. From and after the date of this
Agreement, upon the request of the Purchaser or the Company, each of the Company
and the Purchaser shall execute and deliver such instrument, documents and other
writings as may be reasonably necessary or desirable to confirm and carry out
and to effectuate fully the intent and purposes of this Agreement.

                                       23
<PAGE>   25

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

                                        AVIRON

                                        By: /s/ Fred Kurland
                                           -------------------------------------
                                            Name:  Fred Kurland
                                            Title: Senior Vice President and
                                                   Chief Financial Officer

                                        ACQUA WELLINGTON NORTH
                                        AMERICAN EQUITIES FUND, LTD.

                                        By: /s/ Isser Elishis
                                           -------------------------------------
                                            Name:  Isser Elishis
                                            Title: Chairman and Chief Executive
                                                   Officer

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