<PAGE>

                                                                  Exhibit 10.86

                         [CONFIDENTIAL TREATMENT REQUESTED]

[Certain confidential information has been omitted from the Agreement and filed
separately with the Securities and Exchange Commission pursuant to a request by
Registrant for confidential treatment pursuant to Rule 24b-2.  The omitted
confidential information has been identified by the following statement:
"CONFIDENTIAL TREATMENT REQUESTED".]

Notarial Deed A. Prot. 1996/20
dated 17 February 1996 of the
Notary Public Dr. Werner Wenger, Basle


                                    NOTARIAL DEED
                        -------------------------------------
                          PURCHASE AND ASSIGNMENT AGREEMENT

Negotiated in Basle, Switzerland on the 17th day of February 1996.

Before the notary public Dr. Werner Wenger with place of office in Basle
appeared today:

1.   MR. BERND CROMME, born 8 August 1939, attorney-at-law, of German
     nationality, domiciled at D-65812 Bad Soden,

2.   DR. HANS KUPPER, born 17 July 1944, bio-chemist, of German nationality,
     domiciled at D-35039 Marburg,

     both acting not for themselves, but with a power of attorney for
     BEHRINGWERKE AG, with an office at Marburg (Lahn), registered at the
     commercial register of Marburg (Lahn) under HR B 1055, with notarial
     confirmation of representation, an authenticated copy of which constitutes
     APPENDIX A to this document;

3.   DR. EKKEHARD MOESER, born 20 July 1947, attorney-at-law, domiciled at
     D-60389 Frankfurt am Main, not acting for himself but

     a)   with a power of attorney for 31, CORSA VERWALTUNGSGESELLSCHAFT MBH,
          with an office at Frankfurt am Main, with notarial confirmation of
          representation, the original of which constitutes APPENDIX B to this
          document;


<PAGE>


                                          2


     b)   with a power of attorney for CHIRON CORPORATION, with an office at
          California, with notarial confirmation of representation, the original
          of which constitutes APPENDIX C to this document.

The foregoing persons identified themselves to the notary public by presenting
valid official national identity cards or passports.

Such persons and the notary public declared that they all have sufficient
knowledge of the English language to follow the notarization, which, at the
request of all the parties, will be conducted in English.

Such persons confirmed that they do not wish this document to be translated into
the German language nor do they wish that a German translation of this document
be added as an annex to this document.

From a conversation with such persons, the notary public took evidence that each
of them has sufficient command of the English language to follow and to
understand the document here notarized.

The foregoing persons request that the notary public notarize the following:


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                                          3


                          PURCHASE AND ASSIGNMENT AGREEMENT

between

Behringwerke Aktiengesellschaft,
(hereinafter "Behringwerke")
                                                          - ON THE ONE SIDE -

AND

(1)  31. CORSA Verwaltungsgesellschaft mbH,

     (to be renamed "Chiron Biocine GmbH")

     (hereinafter "Buyer")


(2)  Chiron Corporation,

     (hereinafter "Guarantor")

                                                          - ON THE OTHER SIDE -.

(Behringwerke and Buyer are collectively hereinafter referred to as the
"Parties" or individually as the "Party", as the context requires.)


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                                          4


TABLE OF CONTENTS


Directory of Annexes                                                         5

Preamble                                                                     6

1.   Facts; Covenants                                                        6

2.   Sale and Assignment                                                     7

3.   Put and Call; Shareholders' Agreement                                   8

4.   Purchase Price                                                          9

5.   Condition Precedent                                                    12

6.   Operating Lease Agreement                                              13

7.   Behringwerke's Representation and Warranties                           14

8.   Use of Name                                                            20

9.   Buyer's Representation and Warranties                                  21

10.  Cooperation after the Closing Date                                     22

11.  Non-Competition                                                        22

12.  Confidentiality                                                        23

13.  Merger Control                                                         23

14.  Indemnification; Guarantee                                             24

15.  Miscellaneous                                                          24


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                                          5


DIRECTORY OF ANNEXES

Annex 1.4 (a)    -    Contribution Agreement

Annex 1.4 (b)    -    Partnership Agreement

Annex 3.4        -    Shareholders' Agreement

Annex 4.6        -    Investment Plan for 1996

Annex 4.7        -    Terms and Conditions for Commission

Annex 7.1.16     -    Third Party Consents Agreements

Annex 7.1.18     -    Liens, Pledges, Usufructs and other Encumbrances

Annex 7.1.19     -    Financial Statements

Annex 8          -    Use of Name and Logo

Annex 11         -    Hoechst Letter


<PAGE>

                                          6


PREAMBLE

A.   Object of Behringwerke, a stock company (AKTIENGESELLSCHAFT) incorporated
     under the laws of Germany, is, inter alia, the production and distribution
     of pharmaceutical products for human and animal use.

B.   Object of Buyer, a GmbH organized under the laws of Germany, is the
     distribution of pharmaceutical products for human use.

C.   The Parties propose to enter into a joint venture in the field of human
     vaccines, pursuant to which Behringwerke will contribute its human vaccine
     business (hereinafter the "Business") to a newly organized limited
     partnership (hereinafter "VuCo GmbH & Co."). Buyer will purchase a 49%
     interest in the limited partnership and Buyer will have an option to
     purchase, and Behringwerke will have an option to require Buyer to
     purchase, the remaining 51% interest.

NOW, THEREFORE, the Parties hereto agree as follows:

1.   FACTS; COVENTANTS

1.1  Behringwerke is the sole shareholder of  32. CORSA Verwaltungsgesellschaft
     mbH (hereinafter "VuCo GmbH") and is holding two shares with a nominal
     value of DM 25,000 and DM 25,000  representing 100% of the stated capital
     of VuCo GmbH (hereinafter the "Shares"). VuCo GmbH is registered at the
     commercial register of Amtsgericht Frankfurt a.M. under HR B 40994.


1.2  Behringwerke is the sole limited partner (KOMMANDITISTIN) of VuCo GmbH &
     Co.; application has been filed for registration at the commercial register
     of Amtsgericht Marburg. Behringwerke's limited partnership interest will be
     fully contributed pursuant to the Contribution Agreement as defined in
     clause 1.4; an application has been filed to have registered as liability
     amount of Behringwerke at the commercial register an amount of  DM 70,000
     (in words: Deutsche Mark seventy thousand) (VOLL GELEISTETE
     KOMMANDITEINLAGE UND REGISTRIERTE HAFTEINLAGE).


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                                          7

1.3  Behringwerke is also the sole owner of Institut fur Produkttest und
     Verbrauchsforschung GmbH. ("IPV").

1.4  Presently "IPV" is the sole general partner of VuCo GmbH & Co. Behringwerke
     shall immediately after the date hereof cause VuCo GmbH to replace IPV as
     general  partner of VuCo GmbH & Co. and immediately after such replacement
     Behringwerke shall execute, and shall cause VuCo GmbH & Co. to execute, the
     Contribution Agreement attached as ANNEX 1.4 (a) ("the Contribution
     Agreement") and the limited partnership agreement attached as ANNEX 1.4 (b)
     (the "Partnership Agreement"), the latter with effect as of the Closing
     Date and also to be entered into by Buyer.

2.   SALE AND ASSIGNMENT

2.1  Behringwerke hereby sells to Buyer and Buyer hereby purchases from
     Behringwerke from its share in VuCo GmbH with a nominal value of DM 25,000
     (in words: Deutsche Mark twenty-five thousand) a partial share with a
     nominal value of DM 24,500 (in words: Deutsche Mark twenty four thousand
     five hundred) after split of such share in two shares with nominal values
     of DM 500 (in words: Deutsche Mark five hundred) and DM 24,500  (in words:
     Deutsche Mark twenty-four thousand five hundred). The transfer of the
     purchased share shall have effect as of the Closing Date, subject to the
     occurrence of all of the conditions at the Closing Date as defined in
     clause 5.1. (The sold share in VuCo GmbH is hereinafter referred to as the
     "GmbH Share".) From the Closing Date, Buyer shall be entitled to all
     dividend rights and all other secondary rights of the GmbH Share.

2.2  Behringwerke hereby sells to Buyer and Buyer hereby purchases from
     Behringwerke 49% of its limited partnership interests in VuCo GmbH & Co.
     including 49% of all capital accounts and of any other rights Behringwerke
     may have in VuCo GmbH & Co. (the "Limited Partnership Interest") with
     economical effect as of the Closing Date subject to the occurrence of all
     of the conditions at the Closing Date. Buyer shall be entitled to all
     dividend rights and all other secondary rights of a limited partner of VuCo
     GmbH & Co. with respect to the Limited Partnership Interest.


<PAGE>

                                          8

2.3  Behringwerke hereby assigns to Buyer with effect in rem as of the Closing
     Date the GmbH Share and the Limited Partnership Interest, and Buyer accepts
     such assignment from Behringwerke.

     The effectiveness in rem of the assignment of the GmbH Share and the
     Limited Partnership Interest shall in any case be subject to the condition
     precedent of payment of the Fixed Cash Purchase Price and of the Lease
     Compensation payable to Behringwerke pursuant to clauses 4.1 and 4.2 and
     the other conditions of clause 5.1.

2.4  Behringwerke shall cause VuCo GmbH to consent to the split of the DM 25,000
     share and to the transfer of the Limited Partnership Interest.


3.   PUT AND CALL; SHAREHOLDERS' AGREEMENT

3.1  Behringwerke herewith grants to Buyer the option (the "Chiron Call Option")
     to require Behringwerke to sell to Buyer all of the remaining shares of
     Behringwerke in VuCo GmbH and all of the remaining limited partnership
     interests in VuCo GmbH & Co. (the "Option Interests"). Buyer may exercise
     the Chiron Call Option within each of the following periods: March 1998,
     March 1999, March 2000, March 2001 (the "Call Option Periods").  For the
     purpose of executing the Chiron Call Option Behringwerke hereby irrevocably
     offers to the Buyer to sell the Option Interests within any of the Call
     Option Periods on the terms and conditions set forth herein. Buyer may
     exercise the Chiron Call Option by accepting the offer of Behringwerke by
     notarial deed within each of the Call Option Periods, PROVIDED THAT, Buyer
     gives a notice to Behringwerke 30 days before accepting the offer.

3.2  Buyer herewith grants to Behringwerke the option to require Buyer to buy
     from Behringwerke the Option Interests (the "Behring Put Option").
     Behringwerke may exercise the Behring Put Option within March 2001 (the
     "Put Option Period"). For the purpose of executing the Behring Put Option
     Buyer hereby irrevocably offers to Behringwerke to buy the Option Interests
     within the Put Option Period on the terms and conditions set forth herein.
     Behringwerke may exercise the Behring Put Option by accepting the offer of
     Buyer by notarial deed within the Put Option Period, PROVIDED THAT,
     Behringwerke gives a notice to Buyer 30 days before accepting the offer.


<PAGE>

                                          9


     In case a bankruptcy proceeding or composition proceeding is commenced with
     regard to the assets of VuCo GmbH or VuCo GmbH & Co., or the commencement
     of such proceedings is rejected due to lack of assets, Behringwerke is
     entitled to immediately exercise the Behring Put Option with a notice
     period of thirty days, PROVIDED THAT such notice shall not become effective
     if Buyer arranges that the continuation of VuCo GmbH and VuCo GmbH & Co. as
     a going concern is secured within such notice period.

3.3  Subject to the condition that either the Chiron Call Option or the Behring
     Put Option is exercised pursuant to clauses 3.1 or 3.2 above and subject to
     the further condition that the payment of the Option Purchase Price
     pursuant to clause 4.3 is made, Behringwerke hereby assigns to the Buyer
     the Option Interests and the Buyer accepts such assignment.  Behringwerke
     represents and warrants that as of the effective date of such assignment,
     it is the sole owner of such Option Interests and that the Option Interests
     are fully paid, not repaid and free and clear of any encumbrances and not
     subject to any restrictions on disposition, any preemptive rights, option
     rights, rights of first refusal or similar rights, all with respect to
     rights of third parties.

3.4  Buyer and Behringwerke herewith enter into the Shareholders' Agreement
     attached as ANNEX 3.4 which governs the Parties' shareholder rights in VuCo
     GmbH and VuCo GmbH & Co. for the time period until the exercise of the
     Chiron Call Option or the Behring Put Option.

4.   PURCHASE PRICE

4.1  The purchase price owed by Buyer for the GmbH Share and the Limited
     Partnership Interest is DM 171,500,000 (in words: Deutsche Mark one hundred
     and seventy-one million and five hundred thousand) (hereinafter the "Fixed
     Cash Purchase Price"). The payment of the Fixed Cash Purchase Price is due
     and payable on the Closing Date.

4.2  In addition to the Fixed Cash Purchase Price, Buyer shall pay to
     Behringwerke on the Closing Date 49% of the amount VuCo GmbH & Co. actually
     receives as rent under section 3.1 of the Operating Lease Agreement (the
     "Lease Compensation") entered into pursuant to the Contribution Agreement.

4.3  The purchase price owed by Buyer for the Option Interests is DM 178,500,000
     (in words: Deutsche Mark one hundred seventy-eight million and five hundred
     thousand)


<PAGE>

                                          10


     plus an amount equal to 51% of the Lease Compensation and plus an option
     fee calculated on such amounts at a rate of 5.125 % p.a. (in words: five
     and one eighth percent) compounded annually for the time period between the
     Closing Date and the due date under this clause 4.3 (the "Option Purchase
     Price"). Any dividends (ENTNAHMEN) received by Behringwerke from VuCo GmbH
     or VuCo GmbH & Co., plus interest, if and to the extent appropriate, on
     such amounts at a rate of 5.125 % p.a. (in words: five and one eighth
     percent) compounded annually for the time period between receipt of such
     dividend and receipt of payment under this clause 4.3 shall be credited to
     the Option Purchase Price, if due.

     The Option Purchase Price shall be due and payable within five days of the
     date of the notarization of the acceptance of the Chiron Call Option or the
     Behring Put Option, as the case may be.

4.4  Buyer shall make any payments owed under this clause 4 by wire transfer
     free of cost until 11:00 h at the respective due date to the following
     account of Behringwerke:

                                Commerzbank AG Marburg
                     A/C No. 391 0023 (BLZ/Bank ID-No 533 400 24)

     or any other account as designated by Behringwerke.

4.5  If the Closing Date is deferred for the sole reason that Buyer did not pay
     the full amount of the Fixed Cash Purchase Price and 49 % of the Lease
     Compensation or if Buyer does not pay the Option Purchase Price when due,
     then starting from such date at which the Closing Date otherwise would have
     occurred or the Option Purchase Price was due, the respective amount owed
     by Buyer shall bear interest until receipt of payment at a rate of 3-month
     FIBOR plus 10 basis points p.a.

4.6  The Fixed Cash Purchase Price and the Option Purchase Price include an
     amount of DM 35,000,000 (in words: Deutsche Mark thirty-five million) as
     consideration for the contribution of Stock in VuCo GmbH & Co. by
     Behringwerke pursuant to the Contribution Agreement or the Operating Lease
     Agreement and for investments in the Business which may be activated and
     which are implemented by Behringwerke since 1 January 1996 (the "New
     Investments"). The investments for 1996, as currently planned, approximate
     DM 6,700,000 (in words: Deutsche Mark six million seven hundred thousand)
     and are shown in the investment plan attached as ANNEX 4.6 which
     Behringwerke may alter at its discretion subject to this Agreement and
     the Contribution Agreement at any given time. Behringwerke will consult
     with Buyer from time to time regarding the implementation of


<PAGE>

                                          11



     such plan and any amendments thereto. The Parties shall make an inventory
     close to the Closing Date with respect to such Stock and the New
     Investments. The Parties shall evaluate the Stock and the New Investments
     considering generally accepted accounting principles in Germany and the
     principle of balance sheet consistency. If the value of the Stock and the
     New Investments as determined in accordance with the foregoing provisions,
     exceeds  DM 35,000,000, an amount of 49% of such excess amount shall be
     paid by Buyer to Behringwerke within 4 weeks after the Closing Date. If the
     value of the Stock and the New Investments as determined in accordance with
     the foregoing provisions is lower than DM 35,000,000, an amount of 49% of
     such shortfall shall be paid by Behringwerke to Buyer within 4 weeks after
     the Closing Date. As from the Closing Date any such payment owed by Buyer
     to Behringwerke, or by Behringwerke to Buyer, as the case may be, shall
     bear interest at a rate of 3-month FIBOR p.a. compounded annually. The
     remaining 51% of the balance shall be due and payable by Buyer to
     Behringwerke, or vice versa, as the case may be, at the date of the payment
     under clause 4.3, plus interest at a rate of 5.125% (in words: five and one
     eighth percent) compounded annually for the time period between Closing
     Date and receipt of such balance payment.

4.7  In addition to any purchase price payments hereunder, Buyer agrees to pay
     or to cause VuCo GmbH & Co. to pay to Behringwerke a yearly commission
     ("Commission") on the sales of Buyer's vaccine products listed in ANNEX 4.7
     in Germany calculated as [CONFIDENTIAL TREATMENT REQUESTED] of the excess
     of sales as forecast in ANNEX 4.7.  Any such Commission shall be payable 
     for each of the years through 2001, regardless of the date of exercise 
     of the Chiron Call Option or the Behringwerke Put Option, all further 
     regulated in ANNEX 4.7. To be clear: any such Commission received by 
     Behringwerke will not reduce the Fixed Cash Purchase Price and/or the 
     Option Purchase Price, if any.

4.8  Buyer cannot set off any claims including claims pursuant to clause 7 of
     this Agreement, it may have against any payments under this clause 4 unless
     the counterclaim is undisputed or non-appealable. The exercise of rights of
     retention of Buyer, if any, is also excluded. The same applies to payment
     obligations of Behringwerke pursuant to clause 4.6.

5.   CONDITION PRECEDENT

5.1  The date of perfection (VOLLZUG) of the transactions contemplated in this
     Agreement (the "Closing Date") is subject to the occurrence of each of the
     following conditions:


<PAGE>

                                          12


     5.1.1     VuCo GmbH & Co. is holding all official approvals for the
               operation of the Business as currently conducted pursuant to the
               ARZNEIMITTELGESETZ, GENTECHNIKGESETZ, TIERSCHUTZGESETZ and
               BUNDESSEUCHENGESETZ;

     5.1.2     the Operating Lease Agreement (cf. clause 6) has been terminated
               with effect as of the Closing Date;

     5.1.3     the Contribution Date pursuant to the Contribution Agreement has
               already occurred;

     5.1.4     the approval contemplated in Art. 7 of the Contribution Agreement
               shall have been obtained and the respective other contracting
               party referred to therein shall have consented to an assignment
               of the contract described in ANNEX 7 of the Contribution
               Agreement to VuCo GmbH & Co. (as VuCo GmbH & Co. will exist upon
               purchase of the GmbH Share and the Limited Partnership Interest
               by Buyer contemplated hereby); and

     5.1.5     the necessary merger control approvals pursuant to clause 13 have
               either been granted, regardless of whether subject to any
               conditions, or the implementation of this Agreement cannot be
               prohibited by the merger control authorities due to lapse of
               time.

5.2  The Parties shall use their best efforts that the events stated in clause
     5.1 will be fulfilled as soon as possible and they will promptly inform
     each other of the occurrence of any event stated in clause 5.1. All
     conditions shall be deemed to have occurred as soon as the Parties informed
     each other in writing of such occurrence.
     
5.3  Until Behringwerke shall have obtained the necessary approval referred
     to in clause 5.1.4, either party may initiate the following procedure by
     written notice, which may not be given earlier than 60 (sixty) days after
     the date hereof. If the condition precedent stated in clause 5.1.4 has not
     been fulfilled within such 60 (sixty) days period, each Party shall be
     entitled to terminate this Agreement, effective on five (5) days written
     notice to the other Party, without any Party being obliged to pay or
     entitled to receive any compensation by reason of such termination to or
     from the other Party. Neither Party is entitled to terminate this Agreement
     if  Behringwerke agrees at its own discretion within such period to effect
     a partial universal reorganization or other ways to reorganize in order to
     satisfy such condition and to indemnify Buyer against the cost and expense
     of any challenge regarding the effectiveness of such reorganization to
     cause the succession of VuCo


<PAGE>

                                          13


     GmbH & Co. to the contract described in Annex 7 of the Contribution
     Agreement without the consent of the respective other contracting party.

5.4  This Agreement shall be terminated if Closing Date has not occurred by
     October 31, 1996, unless mutually extended by the Parties.

5.5  On the Closing Date Behringwerke shall cause the managing director(s)
     (GESCHAFTSFUHRER) of VuCo GmbH to resign from office and Buyer and
     Behringwerke shall nominate a new managing director pursuant to the
     Shareholders' Agreement. Buyer shall also render a declaration that it
     waives all claims it or VuCo GmbH or VuCo GmbH & Co. may have against the
     resigning managing director.

5.6  On the Closing Date, Behringwerke shall deliver to Buyer a receipt for the
     purchase price received.

6.   OPERATING LEASE AGREEMENT

     The Operating Lease Agreement as provided for in the Contribution Agreement
     shall in any case become effective and shall run until the Closing Date.
     Behringwerke shall cause VuCo GmbH & Co. to agree to such effectiveness of
     the Operating Lease Agreement.

7.   BEHRINGWERKE'S REPRESENTATION AND WARRANTIES

7.1  Behringwerke represents and warrants in form of an independent guarantee
     (SELBSTANDIGES GARANTIEVERSPRECHEN) as of the date of this Agreement and
     the Closing Date, unless, otherwise stipulated and, excluding any further
     claims, that:

     7.1.1     it has all corporate-legal authorities to conclude and execute
               this Agreement and the execution and implementation of this
               Agreement have duly been authorized by all necessary corporate
               actions, in particular by its supervisory and managing bodies;

     7.1.2     assuming the necessary approvals referred to in clause 13 below
               will be granted and, except for circumstances exclusively within
               the sphere of Buyer, the execution, delivery and performance of
               this Agreement by Behringwerke do not and will not


<PAGE>

                                          14


     7.1.2.1   violate, conflict with or result in the breach of any provision
               of the Articles of Association or GESCHAFTSORDNUNG of
               Behringwerke,

     7.1.2.2   conflict with or violate any law, regulations, order, judgment,
               award, injunction, writ, decree or government order applicable to
               Behringwerke, nor

     7.1.2.3   require the consent of any third party including public
               authorities other than the approvals referred to in clauses 5.1.1
               and 5.1.4;

7.1.3     it is the sole owner of the fully paid in GmbH Share and of the
          Limited Partnership Interest (hereinafter collectively the "VuCo
          Interests") and is entitled to sell and transfer to Buyer the full
          legal and beneficial ownership of the VuCo Interests, and Buyer will
          own such interests

          free and clear from any encumbrances and will thereby become the sole
          owner of the VuCo Interests;

          VuCo GmbH has a net equity (BILANZIELLES REINVERMOGEN - Section 266
          III A HGB) in the amount of at least DM 50,000;

7.1.4     the VuCo Interests are not subject to any restrictions on disposition,
          any preemptive rights, option rights, rights of first refusal or
          similar rights of third parties;

7.1.5     the facts stated in clause 1 are true and correct;

7.1.6     no additional contribution obligations in cash or in kind
          (NACHSCHUBPFLICHTEN) exist with respect to VuCo GmbH and/or VuCo GmbH
          & Co.;

7.1.7     there are no voting trusts, stockholder agreements, proxies or other
          agreements or understandings in effect with respect to the voting or
          transfer of the VuCo Interests except as provided for in the articles
          of incorporation of VuCo GmbH and the Partnership Agreement;

7.1.8     the VuCo Interests do not constitute the entire property of
          Behringwerke within the meaning of sect. 419 of the Civil Code
          (BURGERLICHES GESETZBUCH);

7.1.9     The articles of incorporation (GESELLSCHAFTSVERTRAG) of VuCo GmbH are
          known to the Parties and will only be changed upon mutual consent;


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                                          15

7.1.10    ANNEX 1.4 (b) contains a true and correct copy of the Partnership
          Agreement to be effective on or before the Closing Date;

7.1.11    VuCo GmbH has not conducted any business activities other than
          administration as otherwise expressly contemplateed by this Agreement
          and is not subject to rights or obligations stemming from other
          business activities;

7.1.12    except for the JAHRESPRAMIENORDNUNG; ERFOLGSBETEILIGUNG, neither VuCo
          GmbH nor VuCo GmbH & Co. is bound by any control, profit transfer or
          other agreements of the type referred to in sect. 291, 292 ET SEQ. of
          the Stock Corporation Act (AKTIENGESETZ), and no silent participations
          (STILLE BETEILIGUNGEN), profit participating loans (PARTIARISCHE
          DARLEHEN), profit participations of management or employees or other
          similar obligations exist with respect to the profits of VuCo GmbH
          and/or of VuCo GmbH & Co. except for the Operating Lease Agreement
          (cf. clause 6);

7.1.13    sufficient insurance policies have been concluded and maintained to
          secure against risk arising in connection with the business of VuCo
          GmbH & Co. until the Closing Date; such insurance shall be continued
          for the period of joint ownership, while Hoechst is holding indirectly
          the majority in VuCo GmbH and VuCo GmbH & Co., unless VuCo GmbH & Co.
          and/or VuCo GmbH decides otherwise;

7.1.14    all warranties and representations granted by Behringwerke under the
          Contribution Agreement are true and correct, and Buyer is entitled to
          claim those warranties on behalf of VuCo GmbH & Co.;

7.1.15    between the date of this Agreement and the Closing Date, the
          Contribution Agreement will not be amended, the Business will be
          conducted in the ordinary course and consistent with past practice,
          and Behringwerke shall cause VuCo GmbH and VuCo GmbH & Co. not to
          enter into any transaction outside the ordinary course of business
          without the prior consent of Buyer. As amplification and not
          limitation of the foregoing, VuCo GmbH and/or VuCo GmbH & Co. will
          not:

7.1.15.1  make any loan to, guarantee any indebtedness of or otherwise incur any
          indebtedness on behalf of Behringwerke or any third party or assume
          any other unusual obligations;


<PAGE>

                                          16

7.1.15.2  redeem any of the capital or declare, make or pay any profit
          distributions (whether in cash, securities or other property);

7.1.15.3  enter into any arrangement under or similar to the Transformation Law
          (UMWANDLUNGSGESETZ);

7.1.15.4  purchase any assets or make any investments in excess of DM 50,000 (in
          words: Deutsche Mark fifty thousand), except as described in the
          capital investment plan, without the prior written consent of Buyer;

Behringwerke will not hire new employees attributable to the Business without
the prior consent of Buyer; in case of replacement of leaving employees, such
consent of Buyer shall not be unreasonably withheld;

7.1.16    neither the execution, delivery and performance of this Agreement by
          Behringwerke, the execution, delivery and performance of the
          Contribution Agreement by Behringwerke, VuCo GmbH and VuCo GmbH & Co.,
          nor the consummation of the transactions contemplated hereby and
          thereby, will (i) violate or conflict with Articles of Incorporation
          of Behringwerke or VuCo GmbH or the present partnership agreement of
          VuCo GmbH & Co., (ii) subject to clause 13 violate or conflict with
          any law, regulations, order, judgment, award, injunction, writ or
          decree applicable to Behringwerke, VuCo GmbH or VuCo GmbH & Co., (iii)
          subject to obtaining the third party consents with respect to the
          contracts listed in ANNEX 7.1.16 (the "Third Party Consents"), violate
          or conflict with, result in a breach of, or result in or permit the
          acceleration or termination of or constitute a default under (whether
          with notice or lapse of time or both) any agreement, instrument,
          indenture, mortgage, lien, lease or other contract to which
          Behringwerke, VuCo GmbH or VuCo GmbH & Co. is a party or by which any
          of them or their property or assets is bound, provided such violation,
          conflict, acceleration, termination of default individually or in the
          aggregate would have a material adverse effect on the Business; (iv)
          result in the creation of any lien, charge, or encumbrance on any of
          the property or assets of the Business which individually or in the
          aggregate would have a material adverse effect on the Business;

7.1.17    The Contribution Agreement completely and correctly identifies all
          contracts with licensors, contracts with licensees, leases, employment
          and labor agreements and other contracts relating to the Business
          (other than contracts with an

<PAGE>
                                          17

          annual payment obligation of no more than DM 50,000 and a term of less
          than one year). Except as disclosed in such Annexes, neither VuCo GmbH
          nor VuCo GmbH & Co. is a party or otherwise subject to (i) any
          contract, agreement or instrument evidencing or relating to any
          material amount of indebtedness for borrowed money or the deferred
          purchase price of property, or any direct or indirect guarantee of any
          such indebtedness or deferred purchase price, or (ii) any secrecy or
          other agreement or any injunction, judgment, order or award that (x)
          restricts the right of VuCo GmbH or VuCo GmbH & Co. to engage in any
          place in any line of business or (y) would restrict the right of VuCo
          GmbH or VuCo GmbH & Co. to engage in any place in any line of business
          after the Closing Date;

7.1.18    VuCo GmbH & Co. will receive good and marketable title to the
          intellectual property rights contributed pursuant to clause 3.1.1.1 of
          the Contribution Agreement and to the inventory and other stock
          contributed pursuant to clause 3.1.2 of the Contribution Agreement,
          and will also have good and marketable title to, or a valid leasehold
          interest in, the machinery, equipment and other fixed assets
          contributed pursuant to clause 3.1.1.2 of the Contribution Agreement,
          and except as expressly set forth in the Annexes to such clause or in
          ANNEX 7.1.18, all such assets are free and clear of any liens,
          pledges, usufruct, and other encumbrances;

7.1.19    to the best knowledge and belief of the management board (VORSTAND) of
          Behringwerke and officers (PROKURISTEN) of Behringwerke attributable
          to the Business, the financial statements contained in ANNEX 7.1.19
          fairly present the financial position and results of operation of the
          Business at the respective dates and for the respective periods to
          which they apply;

7.1.20    Behringwerke has disclosed all facts and circumstances which are or
          which can reasonably be expected to be material to Buyer;

7.1.21    Behringwerke, VuCo GmbH and VuCo GmbH & Co. each is in compliance in
          all material respects with all laws, regulations, orders, judgments
          and decrees of any court or governmental or administrative authority
          applicable to the Business so that there will be no material
          detrimental impact for the Business in future;

7.1.22    Since June 30, 1995, there has not been (a) any material adverse
          change in financial condition, operations, business prospects or
          properties of the Business; (b)

<PAGE>

                                          18

          any acquisition or disposition of any of assets of the Business which
          may have a material and adverse effect on the ability of VuCo GmbH &
          Co. to conduct the Business as heretofore conducted; (c) any damage,
          destruction or loss to any properties or assets of the Business which
          may materially and adversely affect or impair VuCo GmbH & Co.'s
          ability to conduct the Business in the manner heretofore conducted; or
          (d) any other act or event outside of the ordinary course of business
          which may materially and adversely affect or impair the ability of
          VuCo GmbH & Co. to conduct the Business in the manner heretofore
          conducted;

7.2  In case of a breach of any of the representations and warranties under
     clause 7.1 the following applies:

     7.2.1     Behringwerke is entitled, with respect to the warranted items, to
               cure the breach. If Behringwerke fails to cure the breach within
               a reasonable period of time, such period not to exceed three
               months after Buyer has notified Behringwerke of the breach, or if
               immediate action is necessary (GEFAHR IM VERZUG), Behringwerke
               shall refund to Buyer the necessary amount spent by Buyer to
               establish the warranted status and this shall be Buyer's sole
               remedy.

     7.2.2     Buyer may only ask for recovery based on a warranty claim or 
               on other claims connected therewith if the individual claim 
               exceeds [CONFIDENTIAL TREATMENT REQUESTED] (in words: 
               [CONFIDENTIAL TREATMENT REQUESTED]) and to the extent the 
               aggregate of all such individual claims exceeds [CONFIDENTIAL
               TREATMENT REQUESTED] (in words: [CONFIDENTIAL TREATMENT
               REQUESTED]). The total amount of the claims here mentioned may
               not exceed [CONFIDENTIAL TREATMENT REQUESTED] (in words: 
               [CONFIDENTIAL TREATMENT REQUESTED]) (the "Warranty Cap"), 
               whereby any warranty claims of VuCo GmbH & Co. pursuant to the 
               Contribution Agreement must be included in calculating the 
               Warranty Cap and the corresponding deductible amounts. This 
               clause 7.2.2 shall not apply with regard to clauses 7.1.1, 
               7.1.2 and with regard to the net equity guarantee pursuant to 
               clause 7.1.3 second paragraph.

7.3  To the extent that Buyer can raise a warranty claim for the same reason
     for which VuCo GmbH & Co. has raised and has got settled a warranty claim
     under the Contribution Agreement, Buyer is excluded to raise its warranty
     claim, notwithstanding that Buyer is entitled to claim those warranties on
     behalf of VuCo GmbH & Co.

7.4  Any claims regarding cancellation (WANDLUNG), rescission (RUCKTRITT) or
     challenge (ANFECHTUNG) of this Agreement or any other release from this
     Agreement, including any

<PAGE>

                                          19

     claim resulting from a liability due to breach of duty prior to contract
     (CULPA IN CONTRAHENDO), are excluded unless Buyer cannot reasonably be
     expected to adhere to this Agreement as a result of the breach of the
     guarantee pursuant to clause 7.1.22.  A breach of clause 7.1.22 by way of
     example and not limitation is considered as occurred if VuCo GmbH & Co's
     business or plant is subject to dislocation or massive destruction of
     production facilities which after insurance proceeds would result in a
     decline in value in excess of DM 52,500,000 (in words: Deutsche Mark 
     fifty-two million five hundred thousand).  Such extraordinary right of
     rescission has to be exercised within two weeks after the Closing Date.

     Any further claims for damages because of a breach of one or more of the 
     guarantees or representations and warranties made pursuant to clause 7 or
     any other liability of Behringwerke as well as claims based on breach of 
     duty prior to contract (CULPA IN CONTRAHENDO) shall be excluded.

7.5  Claims of Buyer pursuant to this clause 7 shall become time-barred fifteen
     (15) months after the Closing Date with the exception of the warranty
     granted under clause 7.1.14 which shall become time-barred as soon as the
     respective warranty claims of VuCo GmbH & Co under the Contribution
     Agreement become time-barred. The limitation period stops running if
     claims are asserted in writing by Buyer against Behringwerke and if the
     reasons on which such claim is based are reasonably identified. If
     Behringwerke does not accept the claim within one month, Buyer must raise
     the claim before court within a further period of three months pursuant to
     clause 15.5 or it becomes time-barred.

8.   USE OF NAME

     Buyer has the royalty free, worldwide exclusive right to use in
     perpetuity the name "Behring" as part of the firm of Buyer, VuCo GmbH
     and VuCo GmbH & Co. and to use such name and the logo "E. v. Behring"
     as described in ANNEX 8, provided, however, that the name and logo may
     only be used in connection with human vaccine products against
     infectious diseases and only in connection with a clear indication of
     the name of Chiron, all as also described in ANNEX 8. Such right to
     use the name Behring and the logo shall be subject to the
     non-exclusive right of Hoechst in India, Sri Lanka and Bangladesh and
     subject to any third parties' rights including not fully controlled
     affiliates.

<PAGE>

                                          20

     The parties will rename VuCo GmbH and VuCo GmbH & Co. within 6 (six)
     months after the Closing Date accordingly.

     Behringwerke is prepared to discuss with Buyer on a case by case basis the
     use of the name Behring in connection with the name Chiron outside of the
     vaccine field for human health care products based on modern biological
     technology (excluding Diagnostics) in as far as this is not in conflict
     with legal aspects and own interests of Behringwerke AG, Hoechst AG, and
     Centeon. All parties will guarantee that all uses will not damage the
     reputation of the name Behring. All discussions hereto will be conducted
     in good faith.

     All uses of the name by either Party will be of high quality and
     consistent with the preservation of the reputation and goodwill associated
     with the name.

     For the avoidance of doubt: Behringwerke shall remain the sole owner of
     the trade name and trademark "Behring" and of the logo "E. v. Behring",
     and all use of such trade name, trademark and logo in accordance with the
     aforesaid shall be governed by a "Trade Name and Trademark License
     Agreement" to be entered into by the relevant parties.

9.   BUYER'S REPRESENTATION AND WARRANTIES

9.1  Buyer represents and warrants in form of an independent guarantee
     (SELBSTANDIGE ERFULLUNGSGARANTIE) excluding any further warranty claims
     that:

     9.1.1     it has all corporate-legal authorities to conclude and execute
               this Agreement and the execution and implementation of this
               Agreement have duly been authorized by all necessary corporate
               actions, in particular by its supervisory and managing bodies;

     9.1.2     assuming the necessary approvals referred to in clause 13 below
               will be granted and except for circumstances exclusively within
               the sphere of Behringwerke, the execution, delivery and
               performance of this Agreement by Buyer do not and will not

               9.1.2.1   violate, conflict with or result in the breach of any
                         provision of the Articles of Association or
                         GESCHAFTSORDNUNG of Buyer,
<PAGE>

                                          21

               9.1.2.2   conflict with or violate any law regulations, order,
                         judgment, award, injunction, writ, decree or government
                         order applicable to Buyer, nor

               9.1.2.3   require the consent of any third party including public
                         authorities.

9.2  In the event that any of the representations and warranties made in clause
     9.1 is incorrect, Buyer shall indemnify Behringwerke for such damage
     Behringwerke may suffer as a result thereof.

10.  COOPERATION AFTER THE CLOSING DATE

10.1 Behringwerke and Buyer agree to cooperate after the Closing Date to achieve
     a smooth and efficient transfer of the VuCo Interests to Buyer.
     Behringwerke and Buyer shall initiate all acts necessary, or cause to be
     initiated such acts, respectively, to implement this Agreement.

10.2 Behringwerke and Buyer shall, without undue delay, pass to each other any
     payment, notice, correspondence, information or inquiry relating to the
     Business which may be received by either of them after the Closing Date
     and which the other is entitled to or is of concern to the other, taking
     into account the terms and conditions of this Agreement. Clause 12 is
     applicable to both Parties in this respect.

11.  NON-COMPETITION

     For a period of five years from the Closing Date, Behringwerke and
     affiliated companies except for VuCo GmbH or VuCo GmbH & Co. shall refrain
     from developing, producing, marketing, selling or otherwise distributing
     human vaccine products in the world; for such purposes an affiliated
     company of Behringwerke is a company in which Behringwerke either holds a
     majority interest or which is controlled by Behringwerke. In the letter
     attached hereto as ANNEX 11 Hoechst AG is undertaking a separate
     non-compete covenant and other covenants with respect to this Agreement
     (the "Hoechst Letter").

<PAGE>


                                          22

12.  CONFIDENTIALITY

     Except as otherwise provided in this Agreement, after the date of this
     Agreement Behringwerke shall not use or disclose to third Parties any
     information disclosed, transferred, assigned, licensed or otherwise made
     available by or to Buyer hereunder and relating to the transfer of the
     Business, unless (i) such information is needed by Behringwerke to
     continue its commercial activities, (ii) is or becomes public knowledge
     through no fault of Behringwerke, (iii) is passed to Behringwerke after
     the Closing Date by a third party which is not under an obligation of
     confidentiality, or (iv) has to be disclosed by Behringwerke pursuant to
     law, judicial, or official order; in such case Behringwerke shall notify
     Buyer in advance about the impending disclosure.

13.  MERGER CONTROL

13.1 Immediately after the date hereof, the Parties' respective counsel shall 
     determine whether this Agreement is subject to the merger control by the 
     Commission of the European Union (hereinafter "Commission") pursuant to
     the Regulation (EEC) No. 4064/89 of the Council of the European
     Communities of December 21, 1989 on the Control of Mergers between
     Undertakings. If so, they will notify the Commission on the merger
     contemplated in this Agreement promptly, but not later than one week after
     the date of notarization. Each party is obligated to provide all
     information and addresses necessary and useful in connection herewith in a
     timely, complete and correct manner and to take all steps necessary and
     useful to achieve a positive outcome of the merger control proceeding.

13.2 All legal acts relating to the consummation of this Agreement are subject
     to the condition precedent that either the Commission has found this
     Agreement to be compatible with the common market or that after the
     notification the prohibition of consummation shall be suspended for
     whatever reason.

     Both Parties shall only be released from the obligation resulting from
     this Agreement in the event that the Commission should deny its approval
     with respect to a transfer of the Business in total. In this context,
     Buyer shall conduct all negotiations with the Commission within due course
     and shall render to the Commission all additional details which shall
     enable the Commission to approve this Agreement, even if under conditions;
     furthermore, Buyer shall offer to the Commission or accept, respectively,
     to implement all acts the Commission deems necessary and shall then
     implement such acts accordingly.

<PAGE>

                                          23

13.3 In case that the Commission forbids the implementation of this Agreement
     in its entirety, the Parties shall regard such decision as final unless
     they agree otherwise until the decision becomes non-appealable.

13.4 In case the German Federal Cartel Office is in charge, clause 13.1 to 13.3
     shall apply respectively.

14.  INDEMNIFICATION; GUARANTEE

14.1 Buyer shall assume responsibility (SELBSTANDIGE ERFULLUNGSGARANTIE) by way
     of fulfillment of all obligations of VuCo GmbH & Co. stemming from the
     Contribution Agreement arising after the Closing Date.

     Buyer shall furthermore indemnify Behringwerke against any liability of
     Behringwerke as (former) limited partner after exercise of the Chiron Call
     Option or the Behring Put Option stemming from any repayment of the
     registered liability amount (HAFTEINLAGE) after the Closing Date.

14.2 The Guarantor shall assume responsibility (SELBSTANDIGEERFULLUNGSGARANTIE)
     by way of fulfillment of all obligations of Buyer stemming from this
     Agreement and its Annexes.

14.3 With respect to the Guarantor's obligation under clause 14.2 , it is
     agreed that the Guarantor shall enter into such reasonable and appropriate
     facilities as the Guarantor, Buyer and Behringwerke may from time to time
     agree.

15.  MISCELLANEOUS

15.1 This Agreement including the Annexes contains the entire understanding of
     the Parties hereto in respect of the subject matter contained herein. No
     agreements other than those expressly set forth herein exist between the
     Parties.

15.2 Any modifications or amendments of this Agreement including this clause
     15.2. shall be effective only if made in writing, unless the law provides
     for a stricter form.

15.3 Each party shall pay its own costs and expenses (including costs and
     expenses of its advisors) incurred in connection with this Agreement and
     the execution of the transac-

<PAGE>

                                          24

     tions contemplated hereby, except for the cost of notarization of this
     Agreement, which shall be borne by Buyer. The expenses for the
     cancellation of encumbrances not assumed by Buyer shall be borne by
     Behringwerke. Any taxes or court expenses and cost in connection with the
     merger control clearance which may arise from implementing this Agreement
     shall be borne by Buyer excluding any taxes based on income or capital
     gain which may arise upon the sale or transfer of the GmbH Share or the
     Limited Partnership Interest from Behringwerke to Buyer, which taxes shall
     remain the obligation of Behringwerke.

15.4 This Agreement shall be governed by and construed in accordance with the
     law of the Federal Republic of Germany (without rules of conflict of
     laws), unless the application of foreign law is compulsory.

15.5 Any disputes arising from, and in connection with, this Agreement shall be
     finally decided by an arbitration court consisting of three arbitrators
     following the rules of arbitration proceedings of the International
     Chamber of Commerce (ICC). The arbitration court shall meet in Frankfurt
     am Main. The language of the proceedings shall be German. The jurisdiction
     of the ordinary courts shall be excluded except for summary judgment
     (EINSTWEILIGER RECHTSSCHUTZ) and writs of execution. The arbitration court
     may also decide about the validity of this document if necessary. The
     costs of any arbitration shall be borne by the Parties pursuant to sect.
     91 et seq. of the Civil Procedure Code (ZIVILPROZEBORDNUNG).

15.6 To the extent possible, each provision of this Agreement will be
     interpreted in such manner as to be effective and valid under the
     applicable law. If any provision of this Agreement is held to be
     prohibited by or invalid under applicable law, such provision will be
     ineffective only to the extent of such prohibition or invalidity, without
     invalidating the remainder of such provision or the remaining provisions
     of this Agreement. To the extent that a provision is ineffective or
     invalid, it shall be replaced by an effective and valid provision which
     comes as close as possible to the economic purpose of the ineffective or
     invalid provision.

15.7 All notices and other communications under this Agreement shall be in
     writing and shall be given or made to the following addresses, unless
     specified otherwise in this contract:
<PAGE>

                                          25

     To Behringwerke:
          Behringwerke AG
          attn. Vorstand
          Postfach 1140
          D-35001 Marburg
          Fax:  (49-6421) 39-4880

     To Buyer/Guarantor:
          Chiron Corporation
          attn. President, Chiron Biocine
          4560 Horton Street
          Emeryville, CA 94608-2916
          U.S.A.
          Fax:  (1-510) 654-5360

          with a copy to General Counsel of Chiron Corporation, same address

15.8 It is agreed that Behringwerke shall cause the Behring/Armour joint
     venture to continue to have distributed in Germany by VuCo GmbH & Co. the
     products currently distributed by Behringwerke on behalf of such joint
     venture on existing terms for so long as VuCo GmbH & Co. is jointly owned.
     Further, it is agreed that the Parties shall cause VuCo
     GmbH & Co. to continue the existing arrangements between Behringwerke
     and Hoechst with respect to the distribution of human vaccine products
     outside Germany at arm's length terms to be agreed upon for not less
     than three years.

15.9 With respect to the Master Service Agreement as attached to the
     Contribution Agreement the following is agreed:

     As contemplated by sections 1.3 and 8.4 of the Master Service
     Agreement, the Services are to be defined in the Annexes and are to be
     divided into categories based upon the length of notice required to be
     given to terminate any such service. Neither the Annexes nor the
     division of the services into categories are complete as of the date
     hereof. The parties agree to complete the Annexes and the
     determination of which Services fall into which categories within six
     months of the Closing Date. Notwithstanding the foregoing the Parties
     agree that the Services will continue uninterrupted after the Closing
     Date. Buyer agrees that Category I will in particular include Services
     such as filling and packaging, production, logistics, materials 
     management, engineering, safety and environment.

15.10After signature of this Agreement, the Parties shall jointly issue a press
     release. Neither party shall, without the prior consultation of the other,
     issue any oral or written statement

<PAGE>

                                          26

     to the press or the public regarding this Agreement, except as required by
     law. This, in particular, applies with respect to the Purchase Price.

The present document with the annexes attached hereto was read aloud in the
presence of the appeared persons and signed by their own hands in my
presence as follows:

Basle, this 17th (seventeenth) day of February 1996 (nineteenhundred-
ninetysix).

<PAGE>


                                                                 ANNEX 1.4 (a)
                                                     to the Purchase Agreement

                                   AGREEMENT
                          ON CONTRIBUTION TO CAPITAL


between

Behringwerke Aktiengesellschaft
Emil-von-Behring-Strasse 76
35041 Marburg

- HEREINAFTER "BEHRINGWERKE" -

a n d

Behring Vakzine GmbH & Co.
Emil-von-Behring-Strasse 76
35041 Marburg

represented by 32. CORSA Verwaltungsgesellschaft mbH in its capacity as general
partner of VuCo GmbH & Co., with same place of business

- HEREINAFTER "VUCO GMBH & CO." -

(Behringwerke and VuCo GmbH & Co. are hereinafter collectively referred to as
the "Parties" or individually as the "Party", as the context requires.)


<PAGE>

                                          2


TABLE OF CONTENTS

Directory of Annexes . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Article 1  -  Contribution . . . . . . . . . . . . . . . . . . . . . . . . 4

Article 2  -  Consideration. . . . . . . . . . . . . . . . . . . . . . . . 4

Article 3  -  Assets and Contracts to be Contributed . . . . . . . . . . . 5

Article 4  -  Transfer of Ownership; Implementation of the Contribution. . 8

Article 5  -  Takeover of Business; Periodical Delimitation. . . . . . . .10

Article 6  -  Warranties . . . . . . . . . . . . . . . . . . . . . . . . .15

Article 7  -  Contracts to be Contributed at a Later Date. . . . . . . . .18

Article 8  -  Use of Name. . . . . . . . . . . . . . . . . . . . . . . . .18

Article 9  -  Transition Period. . . . . . . . . . . . . . . . . . . . . .18

Article 10  -  Operating Lease Agreement . . . . . . . . . . . . . . . . .19

Article 11  -  Contracts to be Concluded . . . . . . . . . . . . . . . . .19

Article 12  -  Tax Law . . . . . . . . . . . . . . . . . . . . . . . . . .19

Article 13  -  Confidentiality . . . . . . . . . . . . . . . . . . . . . .19

Article 14  -  Miscellaneous . . . . . . . . . . . . . . . . . . . . . . .20


<PAGE>

                                          3


DIRECTORY OF ANNEXES

Annex  3.1.1.1 (a)      -    Contributed intellectual property
Annex  3.1.1.1 (b)      -    Licensed intellectual property
Annex  3.1.1.1 (c)      -    License Agreement (in favor of VuCo GmbH & Co.)
Annex  3.1.1.1 (d)      -    License Agreement (in favor of Behringwerke)
Annex  3.1.1.2          -    Fixed assets
Annex  3.1.3.1          -    Contracts with licensors
Annex  3.1.3.2          -    Contracts with licensees
Annex  3.1.3.3          -    Other contracts with third parties
Annex  5.1.1            -    Transferred employees
Annex  6.1.6            -    Shop agreements
Annex  6.1.7            -    Employment contracts with an annual remuneration
                             exceeding DM 300,000
Annex  7                -    Contracts to be contributed at a later time
Annex  10               -    Operating Lease Agreement
Annex  11.1             -    Master Service Agreement
Annex  11.2             -    Lease Agreement


<PAGE>

                                          4

PREAMBLE

Behringwerke and 32. CORSA Verwaltungsgesellschaft have formed VuCo GmbH & Co.
Pursuant to the Purchase and Assignment Agreement between Behringwerke and 31.
CORSA Verwaltungsgesellschaft mbH (to be renamed "Chiron Biocine GmbH") (the
"Purchase Agreement"), Behringwerke undertook the obligation to transfer its
human vaccine unit (the "Business") to VuCo GmbH & Co. as investment in kind.

NOW, THEREFORE, the Parties agree as follows:

ARTICLE 1 - CONTRIBUTION

1.1 As fulfillment of Behringwerke's obligation stemming from the Purchase
    Agreement described in the Preamble, Behringwerke contributes to the
    capital of VuCo GmbH & Co. the Business subject to the terms and conditions
    stated hereinafter and consisting of the assets and contracts described in
    Art. 3 with effect as of 1 April 1996, 00:00 h (the "Contribution Date").

1.2 VuCo GmbH & Co. accepts such contribution.

1.3 The value of the contribution of assets shall be determined pursuant to a
    balance sheet per the Contribution Date (the "Contribution Balance Sheet"),
    which shall include all assets and liabilities, if any, contributed hereby
    and assessed at their respective book values of Behringwerke. The
    Contribution Balance Sheet shall be prepared on a basis consistent with
    that adopted for previous fiscal time periods and in any case in accordance
    with the German generally accepted accounting principles ("GRUNDSATZE
    ORDNUNGSGEMASSER BUCHFUHRUNG UND BILANZIERUNG / GOB"). The Contribution
    Balance Sheet shall be testified by C&L Treuarbeit and the costs shall be
    borne by Behringwerke.

ARTICLE 2 - CONSIDERATION

2.1 Behringwerke shall receive as consideration a fixed capital interest in the
    capital account I kept by VuCo GmbH & Co. in the amount of DM 5,000,000 (in
    words:

<PAGE>

                                          5


    Deutsche Mark five million) as per the Contribution Date (the Kapitalkonto
    I - HAFTEINLAGE "Fixed Capital Interest").

2.2 To the extent that the Contribution Balance Sheet reflects a higher net
    equity value than the Fixed Capital Interest, VuCo GmbH & Co. shall credit
    the surplus in the capital account II of Behringwerke. The same shall apply
    for any subsequent contribution of Stock at the termination date of the
    Operating Lease Agreement (cf. Art. 3.1.2).

ARTICLE 3 - ASSETS AND CONTRACTS TO BE CONTRIBUTED

3.1 The assets and contracts to be contributed (hereinafter collectively
    referred to as the "Vaccine Assets") consist of the following:

    3.1.1 INTANGIBLE/TANGIBLE FIXED ASSETS

          3.1.1.1  All copyrights, patents, trademarks, drug licenses and other
                   intellectual property rights and registrations and
                   applications for registration with respect to any of the
                   foregoing, trade and operational secrets, know-how,
                   procedures, formulas and other intangible assets which are
                   not covered by the aforementioned intellectual property
                   rights, incorporation of such assets and ancillary
                   documents, such as application documents for drug licenses,
                   descriptions, product specifications, production
                   documentation and examination certificates, as well as all
                   sales literature, customers- and suppliers-lists,
                   transferable operational permits and approvals, all of the
                   aforesaid predominantly relating to the Business. The
                   registered intellectual property rights and trademarks are
                   listed in ANNEX 3.1.1.1 (a), which is to be updated as of
                   the Contribution Date and thereafter as provided for in
                   Article 3.2, 3.3 and 3.4;

                   Not part of the intangible assets contributed hereunder are
                   the  rights listed in ANNEX 3.1.1.1 (b) which is to be
                   updated as of the Contribution Date and thereafter as
                   provided for in Article 3.2, 3.3 and 3.4. Behringwerke
                   grants to VuCo GmbH & Co. upon the terms and conditions of
                   the License Agreement attached as ANNEX 3.1.1.1 (c) and
                   concluded herewith a royalty-free license to make use of
                   such rights. In return VuCo GmbH & Co. grants to
                   Behringwerke upon the terms and conditions of the License
                   Agreement attached as ANNEX 3.1.1.1 (d) and concluded
                   herewith a royalty-free license to make use of the rights
                   listed in ANNEX 3.1.1.1 (a) except for the trademarks.


<PAGE>

                                          6


          3.1.1.2  All machinery, equipment, office equipment and other fixed
                   assets including software shown in the books of Behringwerke
                   as being in a cost center related to the Business as listed
                   in ANNEX 3.1.1.2 which is to be updated as of the
                   Contribution Date and thereafter as provided for in Article
                   3.2, 3.3 and 3.4.

    3.1.2 STOCK

          All inventories, finished and semifinished products, raw materials,
          stocks, spare parts, information and promotional material and
          supplies allocated to the Business as well as advance payments for
          products previously sold but still held by Behringwerke, whereby
          Behringwerke shall have the right to exclude such products from
          inventory, all to be identified pursuant to a joint stocktaking close
          to the Contribution Date (hereinafter "Stock"). Stock which is
          produced under a license agreement is contributed and transferred
          subject to the condition subsequent that the respective licensor
          agrees to the transfer of the respective license agreement. In case
          that the respective licensor does not agree to the transfer of the
          respective license agreement, Behringwerke is free to sell such stock
          to any third party. If the Operating Lease Agreement provided for in
          Art. 10 becomes effective, no Stock shall be contributed by
          Behringwerke to VuCo GmbH & Co. pursuant to this Art. 3.1.2.

    3.1.3 CONTRACTS

          The following contracts of Behringwerke as well as offers relating to
          the Business:

          3.1.3.1  contracts with licensors attached as ANNEX 3.1.3.1;

          3.1.3.2  contracts with licensees attached as ANNEX 3.1.3.2;

          3.1.3.3  other contracts with third Parties including, without
                   limitation, with Hoechst and its affiliates other than
                   contracts otherwise dealt with in this Contribution
                   Agreement and/or the Purchase Agreement, attached as ANNEX
                   3.1.3.3, such annex, however, is limited to contracts
                   covering annual payment obligations of more than DM 50,000
                   or having a term of more than one year and not containing
                   purchase orders in the ordinary course of business;

          Behringwerke and VuCo GmbH & Co. shall use their best efforts to
          obtain the consent of the respective contract partners for the
          transfer to VuCo GmbH & Co. with-


<PAGE>

                                          7


          out undue delay after signature of this Agreement. Behringwerke
          herewith grants to VuCo GmbH & Co. a power of attorney to exercise
          all rights stemming from such contracts with respect to the time
          period between the Contribution Date and the date that such consent
          has been granted. As from the Contribution Date, VuCo GmbH & Co.
          shall hold Behringwerke free and harmless in respect of any
          obligations stemming from such contracts.

    3.1.4 All goodwill of and pertaining to the Business, including the right
          to use the name "Behring" in accordance with the further provisions
          of this Agreement.

3.2 As far as assets and contracts attributable to the Business are
    inadvertently not mentioned or not included in the respective Annexes, the
    Parties shall agree on a subsequent transfer or assumption in respect
    thereof and the Parties shall accept such transfer or assumption without
    consideration. Art. 7 remains unaffected.

3.3 As far as assets and contracts not attributable to the Business are
    inadvertently included in the respective Annexes, the Parties shall agree
    on a subsequent retransfer to or reassumption by Behringwerke thereof
    without consideration.

3.4 The exact identity of such Vaccine Assets which are to be identified by
    Annexes shall be governed exclusively by the Annexes updated as of the
    Contribution Date. With respect to ANNEX 3.1.1.1(b) it is agreed that any
    patent applications of Behringwerke filed with the relevant authorities
    within a period of one year after the Closing Date as defined in the
    Purchase Agreement shall be included in such annex and in the respective
    annex of the License Agreement attached as ANNEX 3.1.1.1(c), all subject to
    third parties' rights. With respect to ANNEX 3.1.1.1(a) it is agreed that
    any patent applications of VuCo GmbH & Co. filed with the relevant
    authorities within a period of one year after the Closing Date as defined
    in the Purchase Agreement shall be included in such annex and in the
    respective annex of the License Agreement attached as ANNEX 3.1.1.1(d).

3.5 The above provisions of Article 3.1.1.1 and 3.4 with respect to ANNEX
    3.1.1.1(b) shall apply MUTATIS MUTANDIS to any patents and patent
    applications of Hoechst AG arising out of an ongoing collaboration with
    Behringwerke or relating to existing products of the Business, PROVIDED
    THAT such right shall be granted on reasonable commercial terms, all
    subject to third parties' rights and to the consent of Hoechst AG.


<PAGE>

                                          8


ARTICLE 4 - TRANSFER OF OWNERSHIP; IMPLEMENTATION OF THE CONTRIBUTION

4.1 Behringwerke and VuCo GmbH & Co. are in agreement that the transfer of
    ownership of the Vaccine Assets from Behringwerke to VuCo GmbH & Co. shall
    be effected as of the Contribution Date. VuCo GmbH & Co. is entitled to
    take possession of the movable assets contributed to it under Art. 3.1.1.2
    and of the Stock, if contributed. As far as immediate possession is not
    possible, Behringwerke will possess the items with VuCo GmbH & Co.'s
    approval and according to its instructions (BESITZMITTLER).  As far as the
    movable assets contributed according to Art. 3.1.1.2 are in the possession
    of a third party on the Contribution Date, Behringwerke hereby assigns its
    respective rights and claims it may have against such third party with
    respect to such assets to VuCo GmbH & Co. with effect as of the
    Contribution Date.

4.2 If, due to the retention of title or other security interests of third
    Parties, Behringwerke has rights vested but not yet fully effective
    (ANWARTSCHAFTSRECHTE) with respect to the Vaccine Assets, Behringwerke
    hereby transfers these rights to VuCo GmbH & Co.

4.3 If and to the extent the transfer of ownership or assignment of other
    rights relating to the Vaccine Assets to be contributed requires additional
    acts which are not provided for in this Agreement, the Parties shall
    execute such acts promptly.

4.4 Behringwerke and VuCo GmbH & Co. shall take all action necessary for the
    implementation of this Agreement, including obtaining the necessary
    approvals of public authorities for the transfer of existing permits or
    applying for new permits and soliciting for necessary approvals of contract
    partners or other third parties.

4.5 If and to the extent an assignment of contractual rights and duties cannot
    be effected in relation to third parties, other than provided for in Art.
    7, Behringwerke shall be obliged to exercise the respective contractual
    rights and fulfill obligations in the interest of VuCo GmbH & Co. to the
    extent possible. The same shall apply to the extent necessary and possible
    with respect to the use of public permits. Behringwerke shall internally
    place VuCo GmbH & Co. in the same economic position as it would be in if
    such assignments had been valid and if that is not practicable it shall
    indemnify VuCo GmbH & Co. against all damages associated therewith. VuCo
    GmbH & Co. shall indemnify and internally place Behringwerke in the same
    economic position with respect to the performance by VuCo GmbH & Co.
    directly or indirectly of obligations of Behringwerke under such contracts,
    as though Behringwerke had been discharged from any further liabilities in
    respect


<PAGE>

                                          9


    thereof, but not for any breach caused by the transfer to or assumption by
    VuCo GmbH & Co. of such obligation.

4.6 As of the Contribution Date, all benefits and encumbrances (NUTZEN UND
    LASTEN) related to the Business as well as the risk of accidental loss and
    accidental deterioration of the Business shall pass to VuCo GmbH & Co.

4.7 If due, Behringwerke shall pay all public fees, charges and taxes relating
    to the Business attributable to the time before the Contribution Date,
    irrespective of whether such fees, charges and taxes have been levied at
    the Contribution Date including taxes attributable to the portion of any
    tax period which includes the Contribution Date from the beginning of the
    tax period through the Contribution Date.

4.8 Behringwerke shall pay any and all taxes based on income or capital gain
    imposed as a result of the contribution of assets to VuCo GmbH & Co.
    pursuant to this Agreement.

ARTICLE 5  -  TAKEOVER OF BUSINESS; PERIODICAL DELIMITATION

5.1 With respect to the assumption of employees, the following is agreed:

    5.1.1 As of the Contribution Date, VuCo GmbH & Co. shall assume all rights
          and obligations including pension entitlements, all pursuant to
          Section 613a of the German Civil Code (BGB), arising from the
          employment contracts of the employees of Behringwerke as listed in
          Annex 5.1.1.

    5.1.2 To the extent employees object to the transfer of their employment to
          VuCo GmbH & Co., such employees shall work in the Business until the
          earliest date at which such employments can be terminated, if
          possible, and VuCo GmbH & Co. shall compensate Behringwerke for all
          salaries and fringe payments and other costs related to continuing
          employment. All costs, if any, in connection with the termination of
          such employments shall be borne by Behringwerke. Behringwerke shall
          give priority to investigate whether there are comparable employment
          opportunities within Behringwerke, otherwise the employment of such
          employees shall be terminated with effect as of the earliest date
          possible.


<PAGE>

                                          10


          Behringwerke has the right to nominate employees replacing objecting
          employees with comparable qualification and salary and reasonably
          acceptable to VuCo GmbH & Co. VuCo GmbH & Co. may decline to accept
          such nominees, whether or not reasonably acceptable, but if a
          reasonably acceptable nominee is rejected, then VuCo GmbH & Co. shall
          bear all costs connected with the termination of the employment of
          the objecting employee to be replaced and shall hold Behringwerke
          free and harmless in this respect, unless Behringwerke decides at its
          sole discretion to employ such objecting employee elsewhere in its
          business. If the nominee is accepted, the provisions of this Article
          5 shall apply mutatis mutandis. Starting with the date at which VuCo
          GmbH & Co. employs any replacement employee, Behringwerke shall bear
          all costs connected with an employee who has been replaced because
          she/he objected to the transfer of her/his employment.

    5.1.3 To the extent that VuCo GmbH & Co. has assumed hereunder claims of
          employees pursuant to Section 613a of the German Civil Code (BGB) and
          such claims are attributable to the time prior to the Contribution
          Date, in particular claims for salary (including Christmas and
          vacation pay), vacation claims, bonus claims, settlements (including
          payments for employee inventions), life insurance premiums, and other
          payments to be made in addition to the regular salary, Behringwerke
          shall hold VuCo GmbH & Co. free and harmless therefrom.

    5.1.4 To the extent that VuCo GmbH & Co. has assumed hereunder pension
          obligations for employees pursuant to Section 613 a of the German
          Civil Code (BGB) attributable to the time prior to the Contribution
          Date, Behringwerke shall pay to VuCo GmbH & Co. an amount which
          approximates full cost of the pension liability. Full costs should be
          calculated in accordance with the provisions of FAS 87 using the
          biometric tables of Dr. Klaus Heubeck (amended as follows: mortality
          100%; disability 50%) and applying an interest rate of 7%, future
          salary rate increase of 4% and a fluctuation rate of 15% until age
          30, 10% until age 40, 5% until age 50, and 0% for 50+. The amount
          shall be calculated on the basis of an actuarial report
          (versicherungsmathematisches Gutachten) as of the Closing Date of the
          Purchase Agreement, to be prepared at Behringwerke's cost. Upon
          determination of the amount, such amount shall be payable within ten
          banking days to VuCo GmbH & Co. but in no case prior to the Closing
          Date of the Purchase Agreement.


<PAGE>

                                          11


    5.1.5 Behringwerke shall hold VuCo GmbH & Co. free and harmless against any
          taxes, social security contributions and contributions to workers'
          social associations (Berufsgenossenschaften) to be paid for the
          employees listed in Annex 5.1.1 or replacement employees transferred
          to VuCo GmbH & Co. pursuant to the second paragraph of clause 5.1.2
          attributable to the time period prior to the Contribution Date.

    5.1.6 If any employees other than those listed in Annex 5.1.1 are
          transferred to VuCo GmbH & Co. pursuant to Section 613a BGB,
          Behringwerke shall indemnify VuCo GmbH & Co. against all liabilities
          and expenses arising from such employments. VuCo GmbH & Co. shall
          terminate such employments as soon as legally possible. VuCo GmbH &
          Co. shall take all actions necessary or advisable to minimize any
          such liabilities or expenses of Behringwerke, including, without
          limitation, the use in any legal proceeding of all legal remedies
          available to it and the filing of appeals, all after due consultation
          with Behringwerke. VuCo GmbH & Co. may enter into settlements,
          provided, however, that it shall notify Behringwerke in writing in
          advance of such intention to settle and that Behringwerke does not
          object to such settlement within a period of three weeks after receipt
          of such written notification. The aforementioned provision shall not
          be applicable for the first seven employees who are attributable to
          the Business and have not been listed in Annex 5.1.1 as updated on the
          Contribution Date if and to the extent Behringwerke does not exercise
          its right to nominate replacement employees and VuCo GmbH & Co.
          employs such replacement employees or bears the severance costs.  For
          such seven employees this Art. 5.1 shall apply mutatis mutandis.

5.2  Notwithstanding anything to the contrary contained in this Agreement, VuCo
     GmbH & Co. shall not assume any costs, liabilities or expenses, whether or
     not related to the Business, other than (a) the pension obligations
     expressly assumed under clause 5.1.1, and (b) contractual obligations of
     the Business which accrue after the Contribution Date and which (i) are
     related to the contracts set forth in ANNEXES 3.1.3.1, 3.1.3.2, 3.1.3.3 AND
     7 or (ii) involve expenditures of less than DM 50,000 annually under
     contracts with a term of less than one year, or (iii) are related to
     purchase orders in the ordinary course of Business, or (iv) involve
     expenditures in connection with the License Agreements provided for in
     clause 3.1.1 (the "Assumed Liabilities"). With the exception of the Assumed
     Liabilities, VuCo GmbH & Co. shall not assume or otherwise be responsible
     for any liability or obligation of any nature of Behringwerke, whether or
     not related to the Business, or any claims of such liability or obligation,
     whether matured or unmatured, liquidated or unliquidated, fixed or
     contingent, known or unknown, whether arising out of occurrences prior to,
     at or


<PAGE>

                                          12


     after the Contribution Date. Subject to the foregoing, VuCo GmbH & Co.
     shall be responsible for any liabilities, obligations or damages incurred
     or caused after the Contribution Date in connection with the operation of
     the Business.

5.3  Notwithstanding anything to the contrary contained in this Agreement,
     Behringwerke shall hold VuCo GmbH & Co. free and harmless from all taxes,
     costs, liabilities and expenses related to the Business, in particular
     those arising from the contracts contributed and transferred under Art.
     3.1.3, attributable to the time prior to the Contribution Date. All costs,
     liabilities and expenses related to the Business and which are attributable
     to the time after the Contribution Date shall be borne by VuCo GmbH & Co.
     For the avoidance of doubt: Any capital expenses with respect to
     maintenance, repair and similar works incurred after the Contribution Date
     are attributable to the period after the Contribution Date unless the
     specific works causing the capital expense have been executed prior to the
     Contribution Date; ongoing works shall be split up accordingly.

5.4  All rents, rates, gas, water, electricity, and telecommunication costs,
     ancillary costs and other periodic expenditures relating to the Business
     incurred before the Contribution Date shall be borne by Behringwerke unless
     these are considered expenses related to a certain period after the
     Contribution Date and would therefore be shown as appertainment of payments
     pursuant to sec. 250 para. 1 Commercial Code (HGB) on the asset side. In
     the latter case they shall be borne by VuCo GmbH & Co. On or around the
     Contribution Date, the Parties will determine the uncharged consumption of
     gas, water, electricity, heating and other charges as basis for the
     apportionment of the expenses as stated above. To the extent that an exact
     apportionment is not possible, these expenses will be estimated.

5.5  All incoming payments received before the Contribution Date relating to the
     Business  shall belong to Behringwerke except for incoming payments
     attributable to the time after the Contribution Date which would be shown
     as appertainment of payments pursuant to sec. 250 para. 1 Commercial Code
     (HGB) on the liabilities side. All incoming payments received after the
     Contribution Date relating to VuCo GmbH & Co. shall belong to VuCo GmbH &
     Co. except for incoming payments if attributable to the time before the
     Contribution Date. Receivables attributable to any period starting before
     the Contribution Date and ending after the Contribution Date shall be split
     between Behringwerke and VuCo GmbH & Co. pro rata.

5.6  Behringwerke and VuCo GmbH & Co. shall initiate all action necessary for
     implementation of this Agreement and the takeover of the Business by VuCo
     GmbH & Co.


<PAGE>

                                          13


5.7  Behringwerke and VuCo GmbH & Co. agree to cooperate after the Contribution
     Date to achieve a smooth and efficient transfer of the Business to VuCo
     GmbH & Co.

5.8  Behringwerke and VuCo GmbH & Co. shall, without undue delay, pass to each
     other any payment, notice, correspondence, information or inquiry relating
     to the Business which is received by either of them after the Contribution
     Date and which the other is entitled to or which is of concern to the
     other, taking into account the terms and conditions of this Agreement; Art.
     13 is applicable to both Parties in this respect.

5.9  On or shortly after the Contribution Date or the termination of the
     Operating Lease Agreement, Behringwerke shall hand over to VuCo GmbH & Co.
     all documents, files, books etc., including the personnel files of the
     employees assumed by VuCo GmbH & Co. pursuant to Art. 5.1, except for such
     documents which Behringwerke must keep in its hands for legal reasons.
     Behringwerke hereby permits VuCo GmbH & Co. to review and to take copies of
     all retained documents to the extent necessary to continue the operation of
     the Business. Documents of the Business shall remain Behringwerke's
     property, as far as these are required to exercise rights and meet duties
     arising from the period prior to the Contribution Date, in particular if
     matters of taxation are involved.

5.10 Tax returns relating to the fiscal years prior to the Contribution Date
     are to be prepared by Behringwerke at its costs; with respect to the
     ongoing fiscal year of the Contribution Date, tax returns shall be jointly
     prepared by Behringwerke and VuCo GmbH & Co. and the costs shall be shared
     pro rata temporis. Behringwerke is entitled to designate the accountants
     for testifying the balance sheets and to file any legal remedies against
     levies and/or inspections of the tax authorities and social insurance
     institutions, relating to the time period until the Contribution Date.
     To the extent only VuCo GmbH & Co. can initiate the relevant action, it
     shall do so upon request and as directed by Behringwerke at Behringwerke's
     cost.

5.11 In case the Operating Lease Agreement provided for in Art. 10 becomes
     effective, this Art. 5 shall not be applicable as of the Contribution
     Date but as of such date the termination of the Operating Lease Agreement
     becomes effective, save that Art. 5.1.1 is applicable at both dates.

ARTICLE 6-  WARRANTIES

6.1 Behringwerke hereby warrants and represents in form of an independent
    guarantee (selbstandiges Garantieversprechen), excluding any further claims
    that on the date of signature of this Agreement and as of the Contribution
    Date


<PAGE>

                                          14


    6.1.1 the Vaccine Assets comprise all assets and contracts used in the
          operation of the Business as currently conducted, other than (a) the
          contract listed in Annex 7, which will be governed by the provisions
          of Article 7, (b) certain patent rights which are also used in the
          operation of  Behringwerke's other business units, for which VuCo
          GmbH & Co. will have a royalty-free license to use in accordance with
          the provisions of clause 3.1.1.1, (c) certain machinery, equipment,
          office equipment and other fixed assets which are also used in the
          operation of Behringwerke's other business units; such fixed assets
          will be operated on behalf of the Business by Behringwerke or its
          sub-contractors in accordance with the provisions of the Master
          Service Agreement, (d) certain real property, which will be leased to
          VuCo GmbH & Co. pursuant to the terms of the Lease Agreement, and (e)
          the contracts with Hoechst AG otherwise dealt with in this Agreement
          and/or the Purchase Agreement. Except as expressly set forth in the
          preceding sentence, upon contribution of the Vaccine Assets, VuCo
          GmbH & Co. will have all assets and contracts required for the
          continuation of the operation of the Business by VuCo GmbH & Co.,
          other than public permits that are person-related;

    6.1.2 it has full corporate power and authority to conclude and execute
          this Contribution Agreement, and that the execution and
          implementation of this Contribution  Agreement have been duly
          authorized by all necessary corporate actions, in particular by its
          supervisory and managing bodies;

    6.1.3 it is the sole owner of the respective intellectual property rights
          sold and transferred under Art. 3.1.1.1, except as set forth
          otherwise in the respective Annexes to Art. 3.1.1.1 or in Annex
          7.1.18 of the Purchase Agreement and said rights are free and clear
          of any liens, pledges, usufruct, and other encumbrances except as
          stated in the respective Annexes to Art. 3.1.1.1 and all measures
          necessary to maintain the protection of the intellectual property
          rights have been taken and, to the best knowledge, it does not
          infringe the rights of any other person;

    6.1.4 it is entitled to contribute all assets as provided for under Art.
          3.1.1.2 and that such assets are free and clear of all unusual liens,
          pledges, usufruct, option and use rights or any other encumbrances or
          rights of third parties, unless such encumbrances serve as security
          for obligations assumed by VuCo GmbH & Co. or unless otherwise stated
          in the respective Annexes;


<PAGE>

                                          15


    6.1.5 all public permits object-related, but not person-related, and
          necessary for the operation of the Business have been issued and
          there are no indications that such permits or licenses will be
          limited, recalled or revoked or become subject to new conditions
          (Auflagen), with the exception of those mentioned in the respective
          annexes;

    6.1.6 with respect to the Business no shop agreements
          (Betriebsvereinbarungen) have been concluded with the exception of
          those mentioned in Annex 6.1.6;

    6.1.7 except for those mentioned in Annex 6.1.7, it has not concluded any
          employment contracts attributable to the Business with an annual
          remuneration of more than [CONFIDENTIAL TREATMENT REQUESTED];

    6.1.8 there are no judicial or arbitration proceedings pending or to the
          best of its knowledge threatened with an amount in dispute of more
          than DM 300,000 in the aggregate and, to the best knowledge of the
          Vorstand of Behringwerke, it is not subject to any tax proceedings,
          all only to the extent that there are facts involved that could have
          a material detrimental impact on the Business;

    6.1.9 the Business between 30 June 1995 and the date hereof has been
          conducted in the customary manner, in particular, with respect to
          investments and maintenance of the assets and Stocks and no material
          assets outside the ordinary business have been acquired, sold,
          pledged or otherwise encumbered;

    6.1.10  all pension arrangements for the employees listed in ANNEX 5.1.1
            and transferred to VuCo GmbH & Co. pursuant to Section 613 a Civil
            Code (BGB) and the handling and documentation of respective rights
            including payments thereunder are in accordance with the present
            German legislation; except for those pension plans, no other
            commitments have been made nor additional pension claims exist.

6.2 In case of breach of warranty under Art. 6.1 the following applies:

    6.2.1   With respect to the warranted items Behringwerke is entitled to
            establish the warranted status. If Behringwerke fails to establish
            the warranted status within a reasonable period of time, such
            period not to exceed three months after VuCo GmbH & Co. has
            notified Behringwerke of the breach, or if immediate action is
            necessary (GEFAHR IM VERZUG), Behringwerke shall refund to VuCo
            GmbH & Co. the necessary amount spent by VuCo GmbH & Co. to
            establish the warranted status and this shall be VuCo GmbH & Co.'s
            sole remedy


<PAGE>

                                          16


    6.2.2   VuCo GmbH & Co. may only ask for recovery based on a warranty claim
            or on other claims connected therewith if the individual claim
            exceeds [CONFIDENTIAL TREATMENT REQUESTED] (in words: [CONFIDENTIAL
            TREATMENT REQUESTED]) and the aggregate of all such individual
            claims exceeds [CONFIDENTIAL TREATMENT REQUESTED] (in words:
            [CONFIDENTIAL TREATMENT REQUESTED]). The total amount of the claims
            here mentioned may not exceed [CONFIDENTIAL TREATMENT REQUESTED] (in
            words: [CONFIDENTIAL TREATMENT REQUESTED]) (the "Warranty Cap)",
            whereby any warranty claims of Buyer pursuant to the Purchase
            Agreement must be included in calculating the Warranty Cap and the
            corresponding deductible amounts.

6.3 Beyond the remedies mentioned in this Art. 6, VuCo GmbH & Co. shall have no
    further claims in connection with a breach of a warranty or corresponding
    claims. In particular, to the extent legally possible, all claims of VuCo
    GmbH & Co. going beyond the aforementioned remedies striving for additional
    capital contribution, cancellation (WANDELUNG) or any other form of
    rescission as well as a liability of Behringwerke based on breach of duty
    prior to contract (CULPA IN CONTRAHENDO) are excluded to the extent legally
    possible.

6.4 Claims of VuCo GmbH & Co. under this Art. 6  shall become time-barred
    fifteen (15) months after the Closing Date of the Purchase Agreement. The
    statute of limitation shall be interrupted if claims are asserted in
    writing by VuCo GmbH & Co. against Behringwerke and if the reason on which
    any such claim is based are reasonably identified. If Behringwerke does not
    accept the claim within one month, VuCo GmbH & Co. must raise the claim
    before court within a further period of three months; otherwise it becomes
    time-barred.

ARTICLE 7-  CONTRACTS TO BE CONTRIBUTED AT A LATER DATE

VuCo GmbH & Co. acknowledges that the assignment of rights and duties under the
contracts listed in ANNEX 7 requires the approval of the respective contracting
partner. Behringwerke shall seek to retain the approval for an assumption of
such contracts by VuCo GmbH & Co. If Behringwerke succeeds to obtain the
respective approvals, Behringwerke shall assign all rights and duties under such
contracts listed in ANNEX 7 to VuCo GmbH & Co. and the terms of this
Contribution Agreement shall be applicable to such contracts. If Behringwerke
cannot obtain the approvals, VuCo GmbH & Co shall not be entitled to any
compensation claims.

VuCo GmbH & Co. cannot assert any claims against Behringwerke based on this Art.
7.

ARTICLE 8-  USE OF NAME

Use of the name "Behring" and the logo "E. v. Behring" is governed by clause 8
of the Purchase Agreement.


<PAGE>

                                          17


ARTICLE 9-  TRANSITION PERIOD

Between the date of signature of this Agreement and the Contribution Date
(hereinafter "Transition Period"), Behringwerke shall continue to operate the
Business in the ordinary course, consistent with prior practice and maintain it
as an active operation and shall notify VuCo GmbH & Co. without undue delay upon
becoming aware of any circumstances which (would) lead to a breach of the
warranties set forth in Art. 6. During the Transition Period Behringwerke shall
not employ additional employees attributable to the Business other than such
necessary to replace leaving employees without the prior consent of VuCo GmbH &
Co.

ARTICLE 10-  OPERATING LEASE AGREEMENT

In the event that VuCo GmbH & Co. does not receive the necessary permits prior
to or on the Contribution Date and will thus not be able to continue the
operation of the Business, the Parties enter simultaneously herewith into the
Operating Lease Agreement attached as ANNEX 10.

ARTICLE 11-  CONTRACTS TO BE CONCLUDED

11.1      Behringwerke and VuCo GmbH & Co. enter simultaneously herewith into
          the Master Service Agreement attached as Annex 11.1.

11.2      Behringwerke and VuCo GmbH & Co. enter simultaneously herewith into
          the Lease Agreement attached as Annex 11.2.

ARTICLE 12-  TAX LAW

VuCo GmbH & Co. shall continue the valuation of assets as shown in the tax
balance sheet (STEUERBILANZ) of Behringwerke as of the Contribution Date.
Accordingly, no hidden reserves shall be disclosed and any goodwill shall not be
(newly) activated. The same applies for the commercial balance sheet
(HANDELSBILANZ) for which the book values of the VuCo Assets as determined in
the Contribution Balance Sheet are decisive.


<PAGE>

                                          18


ARTICLE 13-  CONFIDENTIALITY

Except as otherwise provided in this Agreement, after the date of this Agreement
Behringwerke shall not use or disclose to third Parties any information
disclosed, transferred, assigned, licensed or otherwise made available to VuCo
GmbH & Co. hereunder and relating to the transfer of the Business, unless (i)
such information is needed by Behringwerke to continue its commercial activities
or in connection with the Operating Lease Agreement, (ii) is or becomes public
knowledge through no fault of Behringwerke, (iii) is passed to Behringwerke
after the Contribution Date by a third party which is not under an obligation of
confidentiality, or (iv) has to be disclosed by Behringwerke pursuant to law,
judicial, or official compulsion; in such case Behringwerke shall notify VuCo
GmbH & Co. in advance about the impending disclosure.

ARTICLE 14-  MISCELLANEOUS

14.1      This Agreement including the Annexes contains the entire understanding
          of the Parties hereto in respect of the subject matter contained
          herein. No agreements exist other than those expressly set forth
          herein.

14.2      Any modifications or amendments of this Agreement or of any provision
          of this Agreement including this Art. 14.2 shall be effective only if
          made in writing, unless the law provides for a stricter form.

14.3      All expenses incurred in connection with this Agreement and the
          execution of the  transactions contemplated hereby shall be borne by
          Behringwerke.

14.4      This Agreement shall be governed by and construed in accordance with
          the law of the Federal Republic of Germany, unless the application of
          foreign law is compulsory.

14.5      To the extent possible, each provision of this Agreement will be
          interpreted in such manner as to be effective and valid under the
          applicable law. If any provision of this Agreement is held to be
          prohibited by or invalid under applicable law, such provision will be
          ineffective only to the extent of such prohibition or invalidity,
          without invalidating the remainder of such provision or the remaining
          provisions of this Agreement.  To the extent that a provision is
          ineffective or invalid, it shall be replaced by an effective and valid
          provision which comes as close as possible to the economic purpose of
          the ineffective or invalid provision.


<PAGE>

                                          19


Marburg, ______________ 1996



Behringwerke Aktiengesellschaft

by:



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


VuCo GmbH & Co.

by:



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

<PAGE>

                                                              Annex 3.1.1.1(a)
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (5 Pages)


<PAGE>

                                                              Annex 3.1.1.1(b)
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (5 Pages)


<PAGE>

                                                             ANNEX 3.1.1.1 (c)
                                                 to the Contribution Agreement



                                LICENSE AGREEMENT



between

Behringwerke Aktiengesellschaft
Postfach 1140
D-35001 Marburg

(hereinafter "Behringwerke")



and



Behring Vaccine GmbH & Co.

(hereinafter "VuCo GmbH & Co.")


<PAGE>


                                        2



Content
-------


Preamble   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.        Granting of License. . . . . . . . . . . . . . . . . . . . . . . 3

2.        Royalty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3.        Term.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4.        Approval by Contract Partners. . . . . . . . . . . . . . . . . . 5

5.        Covenants by VuCo GmbH & Co. . . . . . . . . . . . . . . . . . . 5

6.        Maintenance of Protected Rights. . . . . . . . . . . . . . . . . 5

7.        Warranties by Behringwerke . . . . . . . . . . . . . . . . . . . 6

8.        Further Developments . . . . . . . . . . . . . . . . . . . . . . 7

9.        Assignment; Sub-Licensing. . . . . . . . . . . . . . . . . . . . 7

10.       Miscellaneous. . . . . . . . . . . . . . . . . . . . . . . . . . 7


<PAGE>

                                   3



PREAMBLE

Pursuant to the "Contribution Agreement" to which this License Agreement is an
annex, Behringwerke is contributing its human vaccine unit (the "Business") to
VuCo GmbH & Co. Some patents of, and actually used by, Behringwerke cannot be
transferred to VuCo GmbH & Co. as its property without restrictions because
these industrial property rights are also used by other units of Behringwerke.

In consideration hereof the parties agree as follows:

     1. GRANTING OF LICENSE

     1.1.   Behringwerke is the holder of the patents and applications for
            registration of patents listed in APPENDIX 1.1 (A) UNDER NO. 1, and
            respective know-how (hereinafter the "Patents").  The term Patent
            shall include continuations, divisionals, continuations-in-part,
            reissues, priority applications, and corresponding foreign
            counterparts.  Furthermore, Behringwerke is co-owner of the patents
            and applications for registration of patents listed in APPENDIX 1.1
            (A) UNDER NO. 2 (hereinafter the "Co-owned/Acquired Patents and Co-
            owned/Acquired Patents hereinafter collectively referred to as the
            "Protected Rights").

     1.2    Behringwerke hereby grants to VuCo GmbH & Co. subject to the terms
            and conditions set forth hereinafter a license or sublicense, as the
            case may be, under the Protected Rights to develop, manufacture, use
            and sell human vaccine products.  As to the Patents, such license
            shall be worldwide and exclusive.  As to the Co-owned/Acquired
            Patents, the territory and degree of exclusivity shall be as
            provided in the relevant agreement, if any, provided that if there
            is no such agreement the license will be worldwide and exclusive,
            all with respect to human vaccine products.


     2. ROYALTY

     The license under the Patents shall be royalty free.  Royalty obligations
     in respect of the development, manufacture, use or sale of human vaccine
     products under


<PAGE>

                                        4



     the Co-owned/Acquired Patents shall flow through directly to VuCo GmbH &
     Co. in the amount specified in the relevant agreement, if any, with no
     addition by Behringwerke.  Payments shall be made directly to the relevant
     licensor or co-owner.  Fixed sum royalties, if any, shall be shared between
     the parties in proportion to their respective use of such Protected Rights
     as measured by net sales of covered products.


3.   TERM

     3.1  This License Agreement becomes effective at the Contribution Date or,
          in case the Operating Lease Agreement becomes effective, upon
          termination of the Operating Lease Agreement.

     3.2  The licenses to the patents included in the Protected Rights shall
          expire on a country-by-country basis with the last to expire Protected
          Right.  The licenses to know-how included in the Protected Rights
          shall continue in perpetuity.  The licenses to Co-owned/Acquired
          Patents shall expire in accordance with the provisions of the relevant
          license agreement.

     3.3  VuCo GmbH & Co. may at any time terminate this License Agreement in
          its entirety or for single Protected Rights with a termination period
          of six months.

     3.4  Behringwerke may also terminate this License Agreement in its entirety
          or for single Protected Rights at any time with a termination period
          of six months, PROVIDED THAT Behringwerke offers to VuCo GmbH & Co. to
          transfer to VuCo GmbH & Co. without consideration all its rights and
          obligations with respect to such Protected Rights to be terminated.
          If VuCo GmbH & Co. accepts such an offer of transfer.  VuCo GmbH & Co.
          shall bear all costs incurred by the transfer. Furthermore,
          Behringwerke may terminate this License Agreement as to the Protected
          Right in question after respective warning and fruitless expiration of
          a period of 30 days after the warning without observing any notice
          period and without an offer to transfer any Protected Rights if VuCo
          GmbH & Co. is in breach of any material clause hereunder and such
          breach makes it unac-


<PAGE>

                                        5



          ceptable for Behringwerke to continue this License Agreement.
          Possible claims for damages by Behringwerke shall not be affected
          hereby.


     4.   APPROVAL BY CONTRACT PARTNERS

          To the extent the consummation of this License Agreement requires
          approvals of third parties under the terms of the agreements for the
          Co-owned/Acquired Patents, Behringwerke shall make every effort to
          receive such approvals without delay after the date hereof.  The
          provisions of Article 4.5 of the Contribution Agreement shall apply
          MUTATIS MUTANDIS to this License Agreement.


     5.   COVENANTS BY VUCO GMBH & CO.

          Within the limits of statutory liability VuCo GmbH & Co. shall
          indemnify and hold Behringwerke free and harmless against any claim
          (other than claims which would be covered by Article 6.1.3 of the
          Contribution Agreement, regardless of when such claims arise) which
          may be brought against Behringwerke by any third parties arising out
          of any use of the Protected Rights by VuCo GmbH & Co., except if such
          damages are caused by willful acts of Behringwerke or its personnel or
          any, licensee or its personnel.


     6.   MAINTENANCE OF PROTECTED RIGHTS

          6.1  For the term of this License Agreement Behringwerke is obligated
               to file, prosecute and maintain the Protected Rights, including
               all interferences and oppositions thereto, at its own cost.  In
               case Behringwerke intends to abandon a Protected Right it shall
               first make an offer of transfer to VuCo GmbH & Co. If the offer
               will not be accepted within 30 days, it shall be deemed to be
               rejected.  In case of acception VuCo GmbH & Co. shall bear all
               further costs.  In case of rejection Behringwerke may abandon the
               Protected Right.  Behringwerke shall make every reasonable effort
               to find a similar solution with respect to the Co-owned/Acquired
               Patents.


<PAGE>

                                        6



          6.2  In the event a third party infringes or may be infringing any of
               the Protected Rights in the field of human vaccines, the parties
               shall confer and consider whether any infringement proceedings
               should be filed against such third party.  Factors to be
               considered include, without limitation, the extent of such
               infringement, the identity of the infringer, the territory in
               question, the strength of the patent in that territory, the
               status of the patent in other territories, the likelihood of
               success, cost and resource allocation, and other possible methods
               of resolution.  The parties  will make every effort to mutually
               agree whether to file any action, including if necessary
               conferring with an independent third party, although in the event
               the parties are unable to agree, the final decision will be made
               by the owner of the patent at issue.  If the parties decide to
               proceed, VuCo GmbH & Co. shall control and bear the costs of such
               proceeding, and shall retain any recovery.  Behringwerke shall
               reasonably cooperate with and assist VuCo GmbH in connection
               therewith.

          6.3  To the extent the use of a Co-owned/Acquired Patent is linked to
               the exercise of an option, Behringwerke hereby authorizes VuCo
               GmbH & Co.to exercise such option in its own name or in the name
               of Behringwerke in order to enable VuCo GmbH & Co. to use the
               respective Protective Rights in accordance with this License
               Agreement. Furthermore, Behringwerke undertakes to make all
               necessary further declarations in order to enable VuCo GmbH & Co.
               to exercise the rights under the respective options. VuCo GmbH &
               Co. shall bear all costs incurred in connection with such
               exercise of options, including any royalty, as long as
               Behringwerke does not use the respective Protected Right. Art. 2
               of this License Agreement shall be applicable.


     7.   WARRANTIES BY BEHRINGWERKE

          Except as expressly set forth in the Contribution Agreement or the
          Purchase Agreement, any warranties and representations of Behringwerke
          are disclaimed.


<PAGE>

                                        7



     8.   FURTHER DEVELOPMENTS

          Except as expressly set forth in clause 3.4 of the Contribution
          Agreement, any new developments/improvements developed by Behringwerke
          or VuCo GmbH & Co. in connection with the Protected Rights remain the
          exclusive intellectual property of the respective party and are not
          subject to any disclosure obligation.  Each party is entitled to
          register such new developments/improvements and to make exclusive use
          of them for its own benefit.


     9.   ASSIGNMENT; SUB-LICENSING

          9.1  VuCo GmbH & Co. may assign or otherwise transfer the rights and
               obligations hereunder in whole or in part to a third party,
               PROVIDED THAT such third party is to be bound by the terms and
               conditions hereof and related hereto.

          9.2  VuCo GmbH & Co. is entitled to grant sub-licenses but restricted
               to the field of human vaccines.

          9.3  Behringwerke is free to assign any or all of its rights and
               obligations hereunder (i) in connection with a corporate
               restructuring, (ii) to Hoechst AG or companies affiliated with
               Hoechst AG or (iii) to an acquiror of the know-how and/or the
               Patents and Co-owned/Acquired Patents.

          9.4  Any assignment, sub-licensing and transfer of the Protected
               Rights is only admissible if the respective recipient undertakes
               to comply with the provisions of this License Agreement.


     10.  MISCELLANEOUS

          10.1 Unless otherwise defined herein, all terms used herein shall have
               the same meanings and definitions as in the Contribution
               Agreement.

          10.2 Unless otherwise specifically amended hereby all other terms of
               the  Contribution Agreement shall remain in full force and
               effect.


<PAGE>

                                        8



          10.3 To the extent possible, each provision of this License Agreement
               will be interpreted in such manner as to be effective and valid
               under the applicable law.  If any provision of this License
               Agreement is held to be prohibited by or invalid under applicable
               law, such provision will be ineffective only to the extent of
               such prohibition or invalidity, without invalidating the
               remainder of such provision or the remaining provisions of this
               License Agreement.  To the extent that a provision is ineffective
               or invalid, it shall be replaced by an effective and valid
               provision which comes as close as possible to the economic
               purpose of the ineffective or invalid provision.

          10.4 Any modifications or amendments of this License Agreement or of
               any provision of this License Agreement shall be effective only
               if made in writing, unless the law provides  for a stricter form.


          10.5 This License Agreement is governed by the laws of the Federal
               Republic of Germany.

          10.6 The exclusive place of jurisdiction shall be Marburg.



Marburg, the_______________



Behringwerke AG by:



____________________________________     ______________________________________


VuCo GmbH & Co. by:



____________________________________     ______________________________________


<PAGE>

                                                             APPENDIX 1. 1 (a)
                                    to License Agreement in favor of VuCo GmbH



                       [CONFIDENTIAL TREATMENT REQUESTED]

                                     (5 Pages)


<PAGE>

                                                              ANNEX 3.1.1.1 (d)
                                                  to the Contribution Agreement



LICENSE AGREEMENT



between

Behringwerke Aktiengesellschaft

Postfach 1140

D-35001 Marburg


(hereinafter "Behringwerke")



and



Behring Vaccine GmbH & Co.

(hereinafter "VuCo GmbH & Co.")


<PAGE>

                                        2



CONTENT


Preamble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
          
1.        Granting of License. . . . . . . . . . . . . . . . . . . . . . .3
          
2.        Royalty. . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
          
3.        Term . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
          
4.        Approval by Contract Partners. . . . . . . . . . . . . . . . . .5
          
5.        Covenants by Behringwerke. . . . . . . . . . . . . . . . . . . .5
          
6.        Maintenance of Protected Rights; Exercise of Options . . . . . .5
          
7.        Warranties by VuCo GmbH & Co . . . . . . . . . . . . . . . . . .6
          
8.        Further Development. . . . . . . . . . . . . . . . . . . . . . .7
          
9.        Assignment; Sub-Licensing. . . . . . . . . . . . . . . . . . . .7
          
10.       Miscellaneous. . . . . . . . . . . . . . . . . . . . . . . . . .8


<PAGE>

                                        3



PREAMBLE

Pursuant to the "Contribution Agreement" to which this License Agreement is an
annex, Behringwerke is contributing its human vaccine unit (the "Business") to
VuCo GmbH & Co. Parts of the assets transferred to VuCo GmbH & Co. are also
patents which Behringwerke or affiliated companies intend to (further) use for
activities outside the Business.

In consideration hereof the parties agree as follows:

     1. GRANTING OF LICENSE

     1.1    Pursuant to the Contribution Agreement Vuco GmbH & Co. will become
            owner of the patents and applications for registration of patents
            listed in APPENDIX 1.1. (a) UNDER NO.1 (the "Patents") and
            respective know-how and a coowner of the patents and applications
            for registration of patents listed in APPENDIX 1.1.(a) UNDER NO. 2
            (hereinafter the "Co-owned/Acquired Patents").  The term Patent
            shall include continuations, divisionals, continuations-in-part,
            reissues, priority applications, and corresponding foreign
            counterparts.  Furthermore, Behringwerke transferred to Vuco GmbH &
            Co. rights and obligations relating to the license and option
            agreements listed in APPENDIX 1.1 (b) (hereinafter the "Licensed
            Patents"). (Patents, Co-owned/Acquired Patents and Licensed Patents
            hereinafter collectively referred to as "Protected Rights").

     1.2    VuCo GmbH & Co. hereby grants to Behringwerke subject to the terms
            and conditions set forth hereinafter a license or sublicense, as the
            case may be, under the Protected Rights to develop, manufacture,
            use, and sell any product other than human vaccine products.  As to
            the Patents, such license shall be worldwide and exclusive.  As to
            the Licensed Patents and the Co-owned/Acquired Patents, the
            territory and the degree of exclusivity shall be as provided in the
            relevant agreement, if any, provided tha that if there is no such
            agreement, the license will be worldwide and exclusive, all with
            respect to any products other than human vaccine products.

            VuCo GmbH & Co. shall have an option to obtain a non-exclusive
            sublicense back from Behringwerke to such Protected Rights on
            commercially


<PAGE>

                                        4



            reasonable terms for uses outside the field of human vaccines, but
            not for diagnostics.

     2. ROYALTY

        The license under the Patents shall be royalty free.  Royalty
        obligations in respect of the development, manufacture, use or sale of
        products under the Licensed Patents and the Coowned/Acquired Patents
        shall flow through directly to Behringwerke in the amount specified in
        the relevant agreement, with no addition by VuCo GmbH & Co.  Payments
        shall be made directly to the relevant licensor.  Fixed sum royalties,
        if any, shall be shared between the parties in proportion to their
        respective use of such protected rights as measured by net sales of
        covered products.

     3. TERM

        3.1    This License Agreement becomes effective at the Contribution Date
               or, in case the Operating Lease Agreement becomes effective, upon
               termination of the Operating Lease Agreement.

        3.2    The licenses to patents included in the Protected Rights shall
               expire on a country-by-country basis with the last to expire
               Protected Right.  The licenses to know-how included in the
               Protected Rights shall continue in perpetuity.  The licenses to
               Licensed Patents shall expire in accordance with the provisions
               of the relevant license agreement.

        3.3    Behringwerke may at any time terminate this License Agreement in
               its entirety or for single Protected Rights with a termination
               period of six months.

        3.4    VuCo GmbH & Co. may also terminate this License Agreement in its
               entirety or for single Protected Rights at any time with a
               termination period of six months, PROVIDED THAT VuCo GmbH & Co.
               offers to Behringwerke to transfer to Behringwerke without
               consideration all its rights and obligations with respect to such
               Protected Rights to be terminated.  If Behringwerke accept such
               an offer of transfer, Behringwerke shall


<PAGE>

                                        5



               bear all costs incurred by the transfer.  Furthermore, VuCo GmbH
               & Co. may terminate this License Agreement as to the Protected
               Right in question after respective warning and fruitless
               expiration of a period of 30 days after the warning without
               observing any notice period and without an offer to transfer the
               Protected Rights, if Behringwerke is in breach of any material
               clause hereunder and such breach makes it unacceptable for VuCo
               GmbH & Co. to continue this License Agreement.  Possible claims
               for damages by VuCo GmbH & Co. shall not be affected hereby.

     4. APPROVAL BY CONTRACT PARTNERS

        To the extent the consummation of this License Ageement requires
        approvals of third parties under the terms of the agreements for
        Protected Rights, the parties shall make any effort to receive such
        approvals without delay after the date hereof.  If any required
        approvals are not granted, the parties will make every effort to agree
        on an alternative solution with equal economic results; VuCo GmbH & Co.
        shall not be obligated to bear any costs thereby incurred.

     5. COVENANTS BY BEHRINGWERKE

        Within the limits of statutory liability Behringwerke shall indemnify
        and hold VuCo GmbH & Co. free and harmless against any claim which
        may be brought against VuCo GmbH & Co. by any third parties arising
        out of any use of the Protected Rights by Behringwerke, except if
        such damages are caused by willful acts of VuCo GmbH & Co. or its
        personnel or any licensee or its personnel.

     6. MAINTENANCE OF PROTECTED RIGHTS; EXERCISE OF OPTIONS

        6.1    For the term of this License Agreement VuCo GmbH & co. is
               obligated to file, prosecute and maintain the Patents and the Co-
               owned/Acquired Patents, including all interferences and
               oppositions thereto, at its own cost.  In case VuCo GmbH & Co.
               intends to abandon a Patent or a Co-owned/Acquired Patent it
               shall first make an offer of transfer to Behringwerke.  If the
               offer will not be accepted within 30 days, it is deemed to be
               rejected.  In case of acception Behringwerke shall bear all
               further costs.  In case of rejection VuCo GmbH & Co. may abandon
               the Protected Right.  VuCo GmbH & Co. shall make any reasonable
               effort to find a similar solution with respect to the Licensed
               Patents.


<PAGE>

                                        6



        6.2    To the extent the use of a Licensed Patent is linked to the
               exercise of an option, Vuco GmbH & Co. hereby authorizes
               Behringwerke to exercise such option in its own name or in the
               name of VuCo GmbH & Co. in order to enable Behringwerke to use
               the respective Protected Rights in accordance with this License
               Agreement.  Furthermore, VuCo GmbH & Co. undertakes to make all
               necessary further declarations in order to enable Behringwerke to
               exercise the rights under the respective options.  Behringwerke
               shall bear all costs, incurred in connection with such exercise
               of options, including any royalty as long as VuCo GmbH & Co. does
               not use the respective Protected Right. Art. 2 of this License
               Agreement shall be applicable.

        6.3    In the event a third party infringes or may be infringing any of
               the Protected Rights other than in the field of human vaccines,
               the parties shall confer and consider whether any infringement
               proceedings should be filed against such third party.  Factors to
               be considered include, without limitation, the extent of such
               infringement, the identity of the infringer, the territory in
               question, the strength of the patent in that territory, the
               status of the patent in other territories, the likelihood of
               success, cost and resource allocation, and other possible methods
               of resolution.  The parties will make every effort to mutually
               agree whether to file any action, including if necessary
               conferring with an independent third party, although in the event
               the parties are unable to agree, the final decision will be made
               by the owner of the patent at issue.  If the parties decide to
               proceed, Behringwerke shall control and bear the costs of such
               proceeding, and shall retain any recovery. VuCo GmbH & Co. shall
               reasonably cooperate with and assist Behringwerke in connection
               therewith.

     7. WARRANTIES BY VUCO GMBH & CO.

        Any warranties and representations of VuCo GmbH & Co. are disclaimed.


<PAGE>

                                        7



     8. FURTHER DEVELOPMENT

        Except as expressly provided in Art. 3.4 of the Contribution Agreement,
        any new developments/improvements developed by Behringwerke or VuCo GmbH
        & Co. in connection with the Protected Rights remain the exclusive
        intellectual property of the respective party and are not subject to any
        disclosure obligation.  Each party is entitled to register such new
        developments/improvements and to make exclusive use of them for its own
        benefit.

     9. ASSIGNMENT; SUB-LICENSING

        9.1    Behringwerke shall not assign or otherwise transfer the rights
               and obligations hereunder to a third party without the prior
               approval of VuCo GmbH & Co. In case Behringwerke sells its
               business operations or part thereof for which the Patents and
               Licensed Patents are needed, VuCo GmbH & Co. shall not withhold
               such approval, unless for good reason.  In any case, Behringwerke
               may transfer all its rights and obligations under this License
               Agreement to Hoechst AG or any company affiliated with Hoechst AG
               pursuant to Sec. 15 et seq. stock corporation act (AKTIENGESETZ)
               without the approval by VuCo GmbH & Co.

        9.2    Behringwerke is entitled to grant sub-licenses, with the
               exception of the production of human vaccines.

        9.3    VuCo GmbH & Co. is free to assign any or all of its rights and
               obligations hereunder (i) in connection with a corporate
               restructuring, (ii) to Chiron Corporation or companies affiliated
               with Chiron Corporation or (iii) to an acquiror of the know-how
               and/or Protected Rights.

        9.4    Any assignment, sub-licensing and transfer of the Protected
               Rights is only admissible if the respective recipient undertakes
               to comply with the provisions of this License Agreement.


<PAGE>

                                        8



    10. MISCELLANEOUS

        10.1   Unless otherwise defined herein, all terms used herein shall have
               the same meanings and definitions as in the Contribution
               Agreement.

        10.2   Unless otherwise specifically amended hereby, all other terms of
               the Contribution Agreement shall remain in full force and effect.

        10.3   To the extent possible, each provision of this License Agreement
               will be interpreted in such manner as to be effective and valid
               under the applicable law.  If any provision of this License
               Agreement is held to be prohibited by or invalid under applicable
               law, such provision will be ineffective only to the extent of
               such prohibition or invalidity, without invalidating the
               remainder of such provision or the remaining provisions of this
               License Agreement.  To the extent that a provision is ineffective
               or invalid, it shall be replaced by an effective and valid
               provision which comes as close as possible to the economic
               purpose of the ineffective or invalid provision.

        10.4   Any modifications or amendments of this License Agreement or of
               any provision of this License Agreement shall be effective only
               if made in writing, unless the law provides for a stricter form.

        10.5   This License Agreement is governed by the laws of the Federal
               Republic of Germany.

        10.6   The exclusive place of jurisdiction shall be Marburg.


<PAGE>

                                        9



Marburg, this _____th day of _______________________________ 1996


Behringwerke AG
by:



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



VuCo GmbH & Co.
by:



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


<PAGE>

                                                                Appendix 1.1(a)
                                  to License Agreement in favor of Behringwerke




                       [CONFIDENTIAL TREATMENT REQUESTED]

                                     (4 Pages)


<PAGE>

                                                                Appendix 1.1(b)
                                  to License Agreement in favor of Behringwerke



                       [CONFIDENTIAL TREATMENT REQUESTED]

                                     (1 Page)


<PAGE>

                                                                 Annex 3.1.1.2
                                                     to Contribution Agreement



This annex 3.1.1.2 is to be prepared by Behringwerke at the time of the
execution of the Contribution Agreement.


<PAGE>

                                                                 Annex 3.1.3.1
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (1 Page)


<PAGE>

                                                                 Annex 3.1.3.2
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (1 Page)

<PAGE>

                                                                 Annex 3.1.3.3
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (3 Pages)


<PAGE>

                                                                    Appendix 1
                                                              to Annex 3.1.3.3
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (3 Pages)


<PAGE>

                                                                   Annex 5.1.1
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (27 Pages)



<PAGE>


                                                                  ANNEX  6.1.6


                                BETRIEBSVEREINBARUNGEN
                                           
                                GRUNDSATZE/RICHTLINIEN
                                           
                                  UBERSICHT/SEITE I
                                           
Nr  Regelungsgageastand:

1.  Einheitliches Entgeltsystem mit Protokollnotizen und Einstufungs -,
    Einarbeitungs - und Durchlaufzeitenregelung

2.  Entgeltfortzahlung im Todesfall

3.  Jahrespramienordnung:  Erfolgsheteiligung

4.  Erschwerniszdlagen

5.  Vermogenswirksame Leistungen

6.  Zuwendungen bei Dienstjubilaen; Offizielle Feierstundo

7.  Gebuhrenerfassung u. abrechnung der Telefonanlage

8.  Werksbusfahrpreis:  SoBe Beschlub zum Werksbusfahrpreis

9.  Altersversorgung, Ende des Arbeitsverhaltnissen

10. Firmenrente; Witwenrente

11. Anderung der Beitragssatze in der Pensionskasse

12. Urlaubsgewahrung, Merkblatt zum aT Urlaubszuschull

13. Zushussee zur beruflichen Weiterbildung

14. Pensionierungsurlaub

15. Freizeitgewahrung fur Umzug

16. Altersfreizeit

17. Grundsatze zur Gewahrung bezahlter and unbezahlter Freistellung,
    Freistellung fur Prufungen

18. Arbeitsunfahigkeitbescheinigungen

<PAGE>

                                                                   ANNEX 6.1.6

                                BETRIEBSVEREINBARUNGEN
                                           
                                GRUNDSATZE/RICHTLINIEN
                                           
                                  UBERSICHT/SEITE 2
                                           

Nr  Regelungsgageastand:

19. Arbeitsordnung und Erganzungen zur Arbeitsordnung

20. Mitarbeitergesprach

21. Verarbeitung personenbezogener Mitarbeiterdaten

22. Durchfuhrung von Abteilungsfeicrn

23. Positive Zeiterfassung u. glcitende Arbeitszeit, Arbeitszcitverkurzungen

24. Grundsatze fur Bildschirmtatigkeit

25. Familie, Beruf, Teilzeit

26. Wahl von Ausbildungsgruppenspreeher

27. Mandatstragerregelung

28. Betriebliche Vertrauensleute

29. Betriebliches Vorschlagswesen

30. Alkohol im Betrieb Liste der Suchthelfer

31. Arbeitssicherhcit und Gesundheitsschutz

32. Ausweisregelung

33. Vorzeitige Pensionierung und Regelungsabrede

34. Neue Techniken

35. StraBenverkchrsordnung;  Parkordnung

36. Grundsatze der Mietgentaltung

<PAGE>

                                                                    ANNEX 6.1.6

                                BETRIEBSVEREINBARUNGEN
                                           
                                GRUNDSATZE/RICHTLINIEN
                                           
                                  UBERSICHT/SEITE 3
                                           

Nr  Regelungsgageastand:

37. Direktversicherung
    Verhutung-von Hepatiris-Infektionen;  Grundsatze zur HIV-Infektion

38. und zur Krannkheit AIDS;  Richtlinien zur Verhutung von Infektionen

39. Verwcndung von Kreditkarten bei Dienstreisen

40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.


<PAGE>

                                                                   Annex 6.1.7
                                                     to Contribution Agreement



                                negative report


<PAGE>

                                                                       Annex 7
                                                     to Contribution Agreement



                          [CONFIDENTIAL TREATMENT REQUESTED]

                                      (1 Page)


<PAGE>

                                                                        ANNEX 10
                                                   to the Contribution Agreement



                              OPERATING LEASE AGREEMENT



between

Behringwerke Aktiengesellschaft
Postfach 1140
D-35001 Marburg

(hereinafter "Behringwerke")


and

Behring Vakzine GmbH & Co.

(hereinafter "VuCo GmbH & Co.).





                                       PREAMBLE

Pursuant to the (Contribution Agreement, of which this Operating Lease Agreement
is an annex, Behringwerke transfers its human vaccines unit (hereinafter the
"Business") to VuCo GmbH & Co. Since VuCo GmbH & Co. needs various permissions
to continue the Business, which it presently does not possess, the parties agree
that Behringwerke shall continue to operate the Business for a transfer period
on the basis of an operating lease agreement.

In consideration hereof, the parties hereto agree as follows:
 

<PAGE>

                                          2



1.  SUBJECT OF AGREEMENT

    Subject of this Operating Lease Agreement is the Business containing all of
    the Vaccine Assets operating property with the exception of the Stock which
    is owned by Behringwerke.


2.  BEGINNING AND DURATION OF THE AGREEMENT


    2.1  The lease shall come into force on the Contribution Date.


    2.2  The lease runs for an indefinite period.

    2.3  This Agreement is deemed to be terminated if all other
         conditions necessary for the occurrence of the Closing Date as defined
         in the Purchase Agreement are satisfied or waived.

    2.4  The right of the Parties to terminate the agreement without
         notice for good cause remains unaffected.


3.  RENT

    3.1  Behringwerke shall have the right to determine the
         amount of the rent as it deems appropriate.  It shall be paid at the
         end of each calendar month.

    3.2  Upon request of Behringwerke, VuCo GmbH & Co. shall submit an invoice
         separately showing the v.a.t.


4.  OPERATION OF BUSINESS

    4.1  As of the Contribution Date. Behringwerke shall operate the Business
         on its own account.

    4.2  Behringwerke is obliged to operate the Business in accordance with
         Art. 9 of the Contribution Agreement.  A sublet is not permitted.
         Behringwerke is not entitled to dispose any of the fixed assets of the
         Business.


<PAGE>

                                          3



    4.3  Behringwerke shall observe the regulations of the Industrial Act
         (Gewerbeordnung), the security regulations and all other regulations
         under public   law.

    4.4  By the end of this Agreement, Behringwerke shall transfer all new
         investments to VuCo GmbH & Co. pursuant to Article 7 para. 2 of this
         Agreement.

    4.5  Behringwerke shall be fully liable for all damages caused in
         connection with the Business and shall hold VuCo GmbH free and
         harmless from all claims in that respect.

    4.6  Behringwerke shall insure the assets in the previous extent.


5.  ASSIGNMENT OF EMPLOYMENT CONTRACTS

    Behringwerke assumes pursuant to sect. 613 a BGB (Civil Code) for the
    duration of this Agreement the entire workforce of the Business and the
    rights and obligations as of the Contribution Date stemming from the
    employment contracts and pension liabilities relating to employees still
    active.

6.  WARRANTY

    Any warranties and representations by VuCo GmbH & Co. are excluded.


7.  TERMINATION OF THE OPERATING LEASE AGREEMENT

    7.1  Upon the termination of this Agreement, the transfer of the Business
         is governed by Articles 4 and 5 of the Contribution Agreement and by
         the regulations set forth hereinafter.

    7.2  At the date of the end of this Agreement, Behringwerke shall transfer
         to VuCo GmbH & Co. the Stock which belongs to the Business and the new
         investments according Article 4 para. 4 of this Agreement.  For this
         purpose, VuCo GmbH & Co. and Behringwerke shall conduct a stock-taking
         of the Stock and of the new investments (hereinafter "Stock-Taking")
         close to the


<PAGE>

                                           4



         day of the termination of this Agreement.  The book value of the
         aforementioned objects shall be credited to capital accounts I and II
         as provided in Art. 2 of the Contribution Agreement.

    7.3  To the extent meaningful, the regulations of the Contribution
         Agreement shall be applicable, mutatis mutandis, with respect to the
         retransfer of the Business to VuCo GmbH & Co.


8.  MISCELLANEOUS

    8.1  Unless otherwise defined herein, all terms shall have the same
         meanings and definitions as in the Contribution Agreement.

    8.2  Unless otherwise specifically amended hereby, all other terms of the
         Contribution Agreement shall remain in full force and effect.

    8.3  To the extent possible, each provision of this Agreement will be
         interpreted in such manner as to be effective and valid under the
         applicable law.  If any provision of this Agreement is held to be
         prohibited by or invalid under applicable law, such provision will be
         ineffective only to the extent of such prohibition or invalidity,
         without invalidating the remainder of such provision or the remaining
         provisions of this Agreement.  To the extent that a provision is
         ineffective or invalid, it shall be replaced by an effective and valid
         provision which comes as close as possible to the economic purpose of
         the ineffective or invalid provision.

    8.4  Any modifications or amendments of this Agreement or of any provision
         of this Agreement including this Art. 8.4 shall be effective only if
         made in writing, unless the law provides for a stricter form.

    8.5  This Agreement is governed by the laws of the Federal Republic of
         Germany.

    8.6  The exclusive place of jurisdiction shall be Marburg.


<PAGE>

                                                                      Annex 11.1
                                                   to the Contribution Agreement



                               MASTER SERVICE AGREEMENT



between


Behringwerke AG

35001 Marburg

- hereinafter "Behringwerke" -


and


Behring Vakzine GmbH & Co.



hereinafter "VuCo GmbH & Co." -


<PAGE>

                                           2



                                       PREAMBLE

A.  Pursuant to the Contribution Agreement to which this Agreement is an Annex
    and to the Purchase and Assignment Agreement entered into by Behringwerke
    and 31. CORSA Verwaltungsgesellschaft mbH (the "Purchase Agreement"),
    Behringwerke is contributing its human vaccine unit (the "Business") to
    VuCo GmbH & Co. VuCo GmbH & Co. will, for the foreseeable future,
    continue to conduct the  Business within the premises of Behringwerke on a
    lease basis.  Therefore, and due to the numerous operational and
    technological interdependencies between the business operations of
    Behringwerke and VuCo GmbH & Co., the Parties agree that both will
    require supply of certain goods and services from the respective other
    Party.

B.  In this Agreement, the Parties wish to stipulate the terms and conditions
    applicable to such supply of goods and services.

C.  In order to facilitate the efficient supply of goods and services by
    Behringwerke to VuCo GmbH & Co. and vice versa and to ensure that each
    Party may plan ahead to remain cost-effective and within the terms and
    conditions set forth herein, it is important that the Parties advise each
    other on a cooperative basis of their requirements and timetables.


Article I - Services Supplied under this Agreement

1.1 Subject to the terms and conditions set forth herein, Behringwerke will
    supply VuCo GmbH & Co. with goods and services listed in ANNEXES (the
    "Behringwerke Services"), VuCo GmbH & Co. will receive and accept such
    Behringwerke Services from Behringwerke.

    Behringwerke may use Hoechst or Centeon Pharma GmbH or affiliates residing
    on Behringwerke's premises or other third parties, the latter only to the
    extent the services do not require the trust of VuCo GmbH & Co. such as
    painting (hereinafter collectively "Internal Partners") as a sub-contractor
    in order to meet its obligations under this Agreement with respect to such
    Behringwerke Service. and nothing in this Agreement shall limit such right
    of sub-contracting.


<PAGE>

                                           3



1.2 Subject to the terms and conditions set forth herein, VuCo GmbH & Co. will
    supply Behringwerke with goods and services listed in ANNEXES - (the `VuCo
    Services"; Behringwerke Services and VuCo Services are hereinafter
    collectively referred to as the "Services").  Behringwerke will receive and
    accept such Services from VuCo GmbH &  Co. It is further understood that
    Behringwerke may pass on and transfer any VuCo GmbH & Co. Services to
    Internal Partners.

1.3 The Services are individually defined as to their nature in Annexes.  All
    Services will be provided in the same amount as provided in 1995, adjusted
    to reflect Behringwerke's projections for 1996: provided, that either Party
    may request an additional amount of any Service, and the provider of such
    Service shall use reasonable commercial efforts to provide such additional
    amount.

1.4 Due to the Business being located within the Behringwerke premises and the
    said technological interdependence, it is mandatory that Behringwerke
    supplies and VuCo GmbH & Co. receives the Behringwerke Services listed in
    ANNEXES - (such as utilities and fire brigades).  VuCo GmbH & Co. will
    receive such Behringwerke Services exclusively from Behringwerke.  For the
    same reasons, it is mandatory that VuCo GmbH & Co. supplies and
    Behringwerke receives the VuCo GmbH & Co. Services listed in ANNEXES - .

    These Services cannot be terminated during the term of the Lease Agreement.

1.5 Services other than those defined in the Annexes hereto are not part of
    this Agreement and may be agreed upon separately in each single case
    pursuant to Art. 1.8. In particular, the Parties will enter into a separate
    lease agreement regarding the use by VuCo GmbH & Co. of parts of
    Behringwerke's premises.

1.6 Whenever one of the Parties and/or any of the Internal Partners needs goods
    and services in addition to those listed in ANNEXES -  and the other Party
    could also be considered as a supplier of such additional goods and
    services, the other Party shall be requested to tender them.  If such goods
    and services are nevertheless obtained from an outside supplier, the other
    Party is to be advised of the reasons for such decision.  At equal cost-
    effectiveness and comparable other terms and conditions, the respective
    other Party shall be preferred to any outside supplier.


<PAGE>

                                           4



1.7 If VuCo GmbH & Co. in addition requires special goods and services which
    are not available or are not available in the desired quality or quantity
    or at the desired time(s), Behringwerke will make every reasonable effort
    to supply these additional goods and services, too, without, however, being
    obliged to do so.  Any additional costs resulting from the supply of these
    additional goods and services will be borne by VuCo GmbH & Co. at a price
    to be negotiated between the Parties.  If the additional goods and services
    are also used by other internal customers of Behringwerke, the additional
    costs will be shared proportionately, based on use, between Behringwerke
    and VuCo GmbH & Co.

1.8 If and when such additional goods and services referred to in Art. 1.6 or
    1.7, above, are purchased from the respective other Party, the respective
    Services shall be listed in new Annexes in the form of ANNEXES -  setting
    forth all information necessary and signed on behalf of each Party by a
    duly authorized signatory (the supply of such goods and services shall be
    considered "Behringwerke Services" or "Vu-Co Services", as the case may be,
    and "Services" in each case) and the provisions of this Agreement shall be
    applicable to such goods and services.


Article 2 - Principles Governing the Supply of Services

2.1 The Parties shall supply the Services in the same kind and quality as if it
    were for captive use (SORGFALT IN EIGENEN ANGELEGENHEITEN).  They will
    allocate qualified staff to the supply of the Services.  Employees
    transferred to VuCo GmbH & Co pursuant to the Contribution Agreement shall
    be deemed qualified for the position held as of the Closing Date.

2.2 Each Party shall observe that the Services supplied by it are supplied, and
    that its operations for which the other Party supplies such Services are
    conducted, in accordance with the applicable legislation.

    The Parties shall observe in particular the technical regulations in
    respect of pharmaceutical products for human use and the products comprised
    in the business of the respective other Party, as well as applicable law,
    ordinances or orders of public authorities.  In addition, the Parties shall
    comply with any health and safety regulations or requirements protecting
    employees and third parties in the sites and buildings or parts thereof
    occupied by the Parties.


<PAGE>

                                           5



2.3 When supplying Services under this Agreement, each Party shall comply with
    the respective other Party's requests as to the specific circumstances of
    such supply to the extent reasonable and possible.  Neither Party is,
    however, obliged to comply with such requests if there are reasons to
    assume that compliance would breach any legislation in force, lead to
    damages to its installations or its property or property of third parties
    or could be associated with exposure to danger of persons.  In such case,
    the respective Party shall promptly inform the other Party of the reasons
    of its concern and discuss appropriate actions with the other Party to
    avoid disadvantages to such other Party as far as reasonably possible.

2.4 If either Party needs official authorization for its supply of Services
    hereunder such Party will prepare the appropriate applications together
    with, and in consultation with, the Party receiving the Services and submit
    them to the authorities.  Behringwerke and VuCo GmbH & Co. will keep each
    other regularly informed on the progress made in such matter and on their
    respective negotiations with the authorities and will discuss in advance
    any necessary measures.

    Behringwerke and VuCo GmbH & Co. shall, in particular, promptly inform each
    other if official action is likely to be initiated which could result in
    the withdrawal or revocation of any authorization for those operations of
    VuCo GmbH & Co. and of Behringwerke which relate to the Services under this
    Agreement.

2.5 Behringwerke and VuCo GmbH & Co. will regularly discuss questions of common
    interest regarding the supply of Services hereunder and regarding those
    units supplying such Services.  Should one of the Parties intend to modify
    its operations in a way which would have significant effects on its future
    need for Services supplied by the other Party, it will inform the other
    Party without delay in order to allow for a joint examination and
    discussion of the effects of such modification on the mutual service
    relationships and to enable the respective other Party to provide an
    initial assessment of the resulting cost increases or reductions to serve
    as a basis for such discussions. In such case, the Parties will make every
    reasonable effort to supply each other with additional amounts of Services
    in the most economical way.


<PAGE>
                                           6



Article 3 - Quantity and Measurement of Services

3.1 Unless otherwise provided for in ANNEXES - , the amount of any Services
    continuously supplied in accordance with such Annexes shall be reviewed by
    the Parties on or before September 30 of each year for the following year.

    To the extent the Parties are unable to reach an agreement on the amount of
    any
    Services to be supplied during the following year, the following applies:

    3.1.1     in case of increased demand, the supplying Party will endeavor to
              meet such demand, but will only be obliged to supply such
              Services in the amount agreed upon for the current year;

    3.1.2     in case of reduced demand, the supplying Party will supply only
              the requested amount of such Services; however, if the supplying
              Party proves that it incurred any residual costs due to such
              reduction, it shall be indemnified by the receiving Party, unless
              otherwise provided for herein.

3.2 Subject to Art. 1.3, the methods, places and other particulars of
    measurement of any measurable Services (e.g., in time, quantities of
    energy, etc.), and the allocation method with regard to any non-measurable
    Services (e.g., security, fire brigade) or for which metering devices are
    not available, are provided for in the respective Annexes.  The Parties
    shall review such provisions as part of the annual review pursuant to Art.
    3.1.


Article 4 - Remuneration

4.1 Services shall be provided at Cost as defined in Art. 4.2.

4.2 "Cost" means the fully burdened, fairly allocated cost of providing the
    relevant Services, which shall include a reasonable return on employed
    capital and reasonable depreciation and amortization of employed assets
    over their useful lives, and a fairly allocated charge for underutilized
    plant and equipment, provided that each Party uses its best efforts to
    employ such plant and equipment otherwise.  Cost shall be determined
    pursuant to reasonable and customary allocation and calculation
    methodologies as consistently applied by Hoechst AG and Guarantor and which
    are consistent with German GAAP; provided that neither Parties' method-


<PAGE>
                                           7



    ologies will be applied in a manner that would cause the Costs charged to
    the other Party to exceed the costs as would be calculated in accordance
    with the methodologies reflected in the financial statements as attached in
    Annex 7.1.19 of the Purchase Agreement.  The Parties will meet and confer
    within three months of the Closing Date, as defined in the Purchase
    Agreement, regarding their respective methodologies.

4.3 Each Party has the right to audit the other Party's books and records by an
    independent Wirtschaftsprufer, at reasonable times and upon reasonable
    notice, solely for the purpose of confirmation of such Party's calculation
    of Costs.  Auditing shall be no more frequent than once a year.

4.4 If either Party believes that the costs of Services provided to it
    hereunder are substantially higher than the costs at which such Services
    generally are available, the Parties shall meet and confer to consider
    appropriate action.


Article 5 - Invoicing and Payment

The Parties' respective financial departments will negotiate reasonable and
appropriate
invoicing and payment terms including compensation for the time value of money.


Article 6 - Liability

6.1 Each Party shall monitor continuously whether the other Party is supplying
    Services in the agreed amount and quality.  Unless otherwise provided in
    the Annexes the following applies: Any incorrect amount and any obvious
    defect shall be notified in writing to the other Party promptly after
    detection. however no later than 30 (thirty) working days after the date on
    which the respective Service was rendered.  Other defects shall be notified
    in writing to the other Party promptly after detection,, however no later
    than 6 (six) months after the date on which the respective Service was
    rendered.  No Party is obliged to accept late notification of complaints.

6.2 The Parties shall only be liable for lack of diligence as applied in their
    own business (SORGFALT IN EIGENEN ANGELEGENHEITEN), Liability for
    consequential damages is hereby excluded.


<PAGE>

                                           8

6.3 In any case, liability of each Party for damages due to, or in connection
    with, Services supplied under this Agreement which are not in accordance
    with the requirements stipulated herein is limited to an amount of
    [CONFIDENTIAL TREATMENT REQUESTED] (in words: [CONFIDENTIAL TREATMENT
    REQUESTED]) per damaging event and to a total of [CONFIDENTIAL TREATMENT
    REQUESTED] (in words: [CONFIDENTIAL TREATMENT REQUESTED]) per calendar year,
    all to the extent legally possible. Such limits are not applicable to the 
    extent the damaging Party can recover compensation for such damages from 
    third parties including insurance companies.

6.4 Damages which amount with respect to a single damaging event to less than
    DM 5,000 (in words: Deutsche Mark five thousand) shall not be recoverable,
    provided that the aggregate amount of such small damages during one
    calendar year is not exceeding DM 25,000 (in words: Deutsche Mark
    twenty-five thousand).


Article 7 - Force Majeure

7.1 Unexpected interruptions in the operations of suppliers, unexpected delays
    in delivery or failure to make deliveries on the part of suppliers,
    strikes, lock outs, official restrictions and other eventualities which
    cannot reasonably be controlled or avoided by the respective Party ("Force
    Majeure") shall relieve such Party to the extent and for the duration of
    such event from its obligations under this Agreement and will not justify a
    claim for damages for any losses suffered by the other Party.

7.2 If a Party is forced to interrupt the supply of Services in whole or in
    part due to Force Majeure and if such situation is foreseeable, such Party
    shall inform the respective other Party promptly of the reasons for, and
    the expected extent and duration of, such interruption.  The Parties will
    make every reasonable effort to keep the negative effects of such an event
    as small as possible.

7.3 After an event of Force Majeure, the Parties shall agree amicably on how
    and to what extent Services not supplied are to be made up.

7.4 If the supply of Services is reduced owing to an event of Force Majeure,
    the respective Party will share the capacity it has available among its
    internal customers, the respective other Party and any other outside
    customers with respect to


<PAGE>

                                           9



         whom it has undertaken obligations, in accordance with the proportion
         of its Services previously accounted for by them.


Article 8 - Duration and Termination

8.1 This Agreement shall commence on the Contribution Date or in case the
    Operating Lease Agreement becomes effective upon the termination of the
    Operating Lease Agreement and shall run indefinitely, unless otherwise
    provided for in this Agreement.

8.2 Either Party may terminate this Agreement with immediate effect with regard
    to the relevant Service(s) if the other Party fails to observe significant
    obligations under this Agreement and does not, within a period of 60
    (sixty) days after having been warned by the other Party in writing to do
    so, return to a course of action which is in line with this Agreement and,
    as far as possible, remedy the infringement of this Agreement.

8.3 Either Party may terminate this Agreement with immediate effect if the
    other Party becomes insolvent or, in particular, if composition or
    insolvency proceedings are instituted with regard to its assets or if such
    procedures have been denied due to lack of assets.

8.4 Furthermore, each Party is entitled to terminate this Agreement, on a
    Service by Service basis, with respect to Services received by it by giving
    prior written notice of termination; provided that no such notice may be
    given before two years in case of category I Services or six months for any
    other Services, all after Closing Date as defined in the Purchase
    Agreement.

         Category I Services: two years prior written notice
         Category II Services: one year prior written notice
         Category III Services: six months prior written notice

8.5 In the event VuCo GmbH & Co. terminates in accordance with Art. 8.4 filling
    and packaging Services less than five years after the Closing Date as
    defined in the Purchase Agreement, and Behringwerke proves that it incurs,
    in connection with such termination, costs which cannot be eliminated even
    though Behringwerke uses its best efforts to reduce or eliminate such costs
    ("Residual


<PAGE>

                                           10



    Costs"), VuCo GmbH & Co. shall compensate Behringwerke for (i) in the first
    year after such termination becomes effective: 50% of such Residual Costs,
    (ii) in the second year: 25%, and (iii) in the third year: 12.5% of such
    Residual Costs.

8.6 In case a Party has - upon specific request of the other Party terminating
    this Agreement partially or entirely - made investments with regard to
    operations rendering Services to the other Party which it would not have
    made without such request, such other Party shall bear 100% of any Residual
    Costs after termination, until such Residual Costs have been completely
    reimbursed.

8.7 The Party claiming Residual Costs shall submit to the other Party a
    detailed record of such Residual Costs by the end of each calendar quarter.

8.8 The Residual Costs shall be invoiced separately for each month and shall
    become due and payable on the 15th day of the month  following the date on
    which the respective other Party receives such invoice.  Art. 4.3 shall
    apply MUTATIS MUTANDIS.

8.9 Any notice of termination of this Agreement, in its entirety or in part,
    shall only be valid if given in writing.

8.10     In case that either Party terminating Services wishes to establish its
         own functions with regard to such Services, it shall give priority to
         employees of the existing functions of the respective other Party.

8.11     Upon notice of termination of any Services hereunder, the Parties shall
         meet and confer regarding reasonable and appropriate steps to minimize
         the impact of such termination on remaining operations, in particular
         the possibility of gradually phasing out such Services over the course
         of the termination period.


Article 9 - Confidentiality

9.1 Any information whether written, oral or otherwise provided by a Party or a
    Party's sub-contractor to the other Party and any information obtained by a
    Party in connection with this Agreement, including the terms and conditions
    of this Agreement, shall be treated as confidential by the Party, receiving
    such information, shall only be used for purposes consistent with this
    Agreement and shall not


<PAGE>

                                           11

    be disclosed to any third party unless the Party or sub-contractor who
    provided such information has given its prior written consent to such other
    use or disclosure; provided, however, that each Party may disclose such
    information for purposes consistent with this Agreement to its employees,
    agents and sub-contractors, if any such employee, agent or sub-contractor
    agrees to keep such information confidential as if it were a party hereto.

9.2 The obligations of confidentiality, including the obligations of restricted
    use, shall continue for a period of ten years after the termination of this
    Agreement.

9.3 Excluded from the restrictions provided for in Art. 9.1 and 9.2 above is
    all information that has been disclosed by one Party or a sub-contractor to
    the other Party and which is:

    9.3.1     information that such other Party possessed in its own right
              before disclosure by the first Party or the sub-contractor;

    9.3.2     information that is in the public domain at the time of
              disclosure by a Party or a sub-contractor or has become part of
              the public domain through no fault of the other Party having
              received such information;

    9.3.3     information that such other Party has received, without
              restriction on its disclosure, legitimately from a third party
              not deriving the same from the Party or sub-contractor who made
              the original disclosure.

9.4 Information which is necessary for the enforcement of this Agreement or for
    compliance with applicable law, ordinances or orders of public authorities
    may be disclosed accordingly, provided that all reasonable steps are taken
    to preserve the confidentiality and the restricted use of such information.

9.5 All drawings, plans and other documents produced or commissioned by a Party
    or sub-contractor regarding any Service to be rendered shall remain the
    property of such Party or sub-contractor, unless agreement to the contrary
    has been reached.  Subject to Art. 9.3, such documents and any other
    confidential information received and any copies thereof shall be destroyed
    or returned upon request of the disclosing Party or sub-contractor or in
    the event of termination or rescission of this Agreement in total or in
    part.


<PAGE>

                                           12



Article 10 - Governing Law; Arbitration

10.1     This Agreement shall be governed by, and construed in accordance with,
         the law of the Federal Republic of Germany.

10.2     In case of any question or difference which may arise concerning the
         validity, construction, meaning or effect of this Agreement or
         concerning the rights and liabilities of the Parties hereunder or any
         matter arising out of, or in connection with, this Agreement cannot be
         amicably resolved, such question or difference shall be referred to,
         and determined by, an ad hoc arbitration tribunal of three arbitrators
         (the "Tribunal").

10.3     The arbitrators shall be appointed as follows:

    10.3.1    each party shall appoint one arbitrator, and the two arbitrators
              so appointed shall appoint a third arbitrator who shall be
              qualified to sit as a judge (Befahigung zum Richteramt) and who
              shall act as president of the Tribunal;

    10.3.2    if either Party fails to appoint its own arbitrator within
              twenty-one days of receipt of a written request by the other
              Party or if the two arbitrators are unable to jointly select a
              president within twenty-one days from the last appointment, such
              arbitrator or president shall be appointed by the President of
              the Court of Appeal of Frankfurt am Main (Prasident des
              Oberlandesgerichts) at the request of either Party.

10.4     The venue of such arbitration shall be Frankfurt am Main and the
         language shall be German.

10.5     The award of the Tribunal, which shall state the reasons for the
         decision, shall be final and binding upon the Parties.  The
         arbitrators shall have power to direct any interim measures.

10.6     With respect to aspects not expressly stipulated in this Art. 10, the
         arbitration shall be in accordance with the rules
         (Schiedsgerichtsordnung) of the Deutsche Institute for
         Schiedsgerichtswesen e.V.


<PAGE>

                                           13



Article 11 - Access to Behringwerke-Premises

11.1 With regard to the access to the Behringwerke-premises by employees of VuCo
     GmbH & Co. and/or third parties doing business with VuCo GmbH & Co. the
     following applies:

    11.1.1    At the entrance to the premises controls will be held in
              accordance with the Behringwerke-guidelines as amended from time
              to time.  To the extent technical appliances are required (e.g.,
              code cards), the specifications of which have to be agreed upon
              with Behringwerke, VuCo GmbH & Co. shall obtain such appliances
              at its own cost, to the extent possible by law.  It is VuCo GmbH
              & Co.'s responsibility that any orders of Behringwerke control
              personnel are followed and that the specific identification
              requirements imposed by Behringwerke under its guidelines are
              met.

    11.1.2    In order to meet the obligations hereunder, buildings, plants and
              parts of the Behringwerke-premises not expressly designated for
              such purpose may only be entered with the consent of
              Behringwerke.

11.2 VuCo GmbH & Co. undertakes to comply with the Behringwerke-guidelines, as
    applicable at any given time, to the use of its premises, in particular
    those regarding fire prevention, security or traffic in non-public areas.
    Such obligation is applicable also to VuCo GmbH & Co. personnel and to
    third parties doing business with VuCo GmbH & Co.; and VuCo GmbH & Co.
    shall inform such third parties of said obligations and guidelines.


Article 12 - Final Provisions

12.1 Unless otherwise defined herein, all terms shall have the same meanings and
    definitions as those in the Contribution Agreement.

12.2 Unless otherwise specifically amended hereby, all other terms of the
     Contribution Agreement shall remain in full force and effect.

12.3 Any rights of set-off (Aufrechnung) and/or retention (Zuruckbehaltung)
    based on claims for damages under this Agreement shall be excluded unless
    such claims


<PAGE>

                                           14



    are undisputed between the Parties or confirmed by a non-appealable
    court/arbitration decision.

12.4 Each Party may only assign this Agreement to a fully controlled affiliate
    which has the means to fulfill the obligations under this Agreement.

12.5 From time to time after the date hereof, at the request of either Party,
    the Parties shall execute and deliver to such requesting Party such
    documents and take such other action as such requesting Party may
    reasonably need in order to consummate more effectively the transactions
    contemplated hereby and to satisfy any legal requirements.

12.6 Any notification or amendment to this Agreement, including this Art. 12.6,
    must be in writing in order to be valid, unless more stringent requirements
    as to the form are stipulated by applicable law.

12.7 The Annexes hereto will become integral parts of this Agreement, and all
    references herein to this "Agreement" shall also include the Annexes.

12.8 To the extent possible, each provision of this Agreement will be
     interpreted in such manner as to be effective and valid under the
     applicable law.  If any provision of this Agreement is held to be
     prohibited by or invalid under applicable law, such provision will be
     ineffective only to the extent of such prohibition or invalidity, without
     invalidating the remainder of such provision or the remaining provisions
     of this Agreement. To the extent that a provision is ineffective or
     invalid, it shall be replaced by an effective and valid provision which
     comes as close as possible to the economic purpose of the ineffective or
     invalid provision.


________________,this ___ day of _______,1996.


BEHRINGWERKE AG                             [VuCo GmbH & Co.]


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


<PAGE>

                                                                      ANNEX 11.2
                                                   to the Contribution Agreement



LEASE AGREEMENT

between



Behringwerke AG
35001 Marburg

- hereinafter "Behringwerke" -


and


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


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

- hereinafter "VuCo GmbH & Co." -


<PAGE>

                                        2


                                TABLE OF CONTENTS

Preamble                                                                     4

Article 1 - Object of Lease                                                  4

Article 2 - Term of Lease                                                    5

Article 3 - Rent                                                             5

Article 4 - Ancillary Costs                                                  6

Article 5 - Value Added Tax                                                  8

Article 6 - Condition of the Premises                                        8

Article 7 - Liability, Encumbrances, Responsibility                          8

Article 8 - Insurance                                                        9

Article 9 - Use of Premises                                                 10

Article 10 - Maintenance and Repairs                                        12

Article 11 - Destruction of Premises                                        12

Article 12 - Structural Changes by Behringwerke                             13

Article 13 - Assignment and Subletting                                      13

Article 14 - Change of legal entity, Sale of Business                       14

Article 15 - Signs                                                          14

Article 16 - Indemnification                                                14

Article 17 - Default, Termination                                           15

Article 18 - Hazardous Materials                                            17

Article 19 - Force Majeure                                                  18

Article 20 - Confidentiality                                                18



<PAGE>

                                        3


Article 21 - Arbitration                                                    19

Article 22 - Final Provisions                                               20



<PAGE>

                                        4

                                    PREAMBLE

Pursuant to the Contribution Agreement to which this Lease Agreement is an
annex, Behringwerke is contributing its human vaccine unit (the "Business") to
VuCo GmbH & Co. VuCo GmbH & Co. intends, for the foreseeable future, to conduct
the Business within the premises of Behringwerke on a lease basis.

Therefore, the parties hereto agree as follows:

ARTICLE 1 - OBJECT OF LEASE

1.1  Behringwerke hereby leases to VuCo GmbH & Co. and VuCo GmbH & Co. hereby
     leases from Behringwerke certain parcels rentable land offices space,
     production facilities including fixtures and integral parts (WESENTLICHE
     BESTANDTEILE) within Behringwerke's Marburg sites which are particularly
     described and fully enumerated in ANNEX 1.1, (a) and marked in black in
     ANNEX 1.1, (b) (the "Premises"). Under this lease, VuCo GmbH & Co. is also
     entitled to enter and use common areas (GEMEINFLACHEN), designated access
     and delivery areas, if any, waste disposal facilities and access to ingress
     and egress of the site, to parking spaces, and to the cafeteria, subject to
     Behringwerke-guidelines which shall be exercised by Behringwerke in
     accordance with sect. 315 et seq. Civil Code (BGB).

1.2  The Premises shall be occupied and used by VuCo GmbH & Co. for the business
     of human health care and shall not be used for any other purpose whatsoever
     without the prior written consent of Behringwerke, which shall not be
     unreasonably withheld.

     Any consent by Behringwerke, even if not explicitly stated, shall always be
     granted subject to all official authorizations as may be required for the
     envisaged change of the use of the Premises. Upon request, VuCo GmbH & Co.
     shall provide Behringwerke with proof that all necessary official
     authorizations have been duly granted.

1.3  The supply of utilities and services such as electricity, water etc. by
     Behringwerke and VuCo GmbH & Co.'s obligation to receive, and pay for, any
     such utilities and services are specifically settled in the Master Service
     Agreement.

ARTICLE 2 - TERM OF LEASE

2.1  The Lease shall commence on the Contribution Date or, in case the Operating
     Lease Agreement (BETRIEBSPACHTVERTRAG) becomes effective, upon termination
     of the Operating 


<PAGE>

                                        5


     Lease Agreement (the "Closing Date"). The initial term of the lease shall
     be five years (the "Initial Term"). VuCo GmbH & Co. shall have the right in
     its discretion to extend the lease for an additional five years (the
     "Extension Period") by providing written notice to Behringwerke no later
     than March 31, 2001.

     During the Extension Period, VuCo GmbH & Co. shall have the right to
     terminate the lease in whole or in certain parts of the Premises upon six
     months' prior written notice to Behringwerke. During the Initial Term, VuCo
     GmbH & Co. shall have the right to terminate the lease in part (but not in
     whole) upon six months' prior written notice to Behringwerke, PROVIDED THAT
     such right of early termination shall not apply to Premises used for
     manufacturing including quality control. 

     In case Behringwerke undertook capital investments related to the Premises
     in the Extension Period on specific written request of VuCo GmbH & Co. and
     VuCo GmbH & Co. terminates this Agreement under the foregoing sentence,
     VuCo GmbH & Co. shall reasonably compensate Behringwerke therefore.

2.2  Section 568 German Civil Code (Section 568 BGB) shall not apply upon expiry
     of the term of the Lease.

ARTICLE 3 - RENT

3.1  As of the Closing Date VuCo GmbH & Co. shall pay to Behringwerke as annual
     rent an amount to be calculated on the basis of present lease agreement
     agreed between Behringwerke and Hoechst but in no case more than fair
     market value. For this purpose VuCo GmbH & Co. has the right to audit
     Behringwerke books and records of an independent Wirtschaftsprufer
     acceptable for Behringwerke at reasonable times and upon reasonable notice
     solely for the purpose of confirmation of such Party's calculation of
     costs. Auditing shall be no more frequent than once a year.

     In case the Parties cannot agree on the fair market rent either Party is
     entitled to request the President of the chamber of commerce of Frankfurt
     to nominate an expert who shall resolve such matter to be binding upon the
     Parties. The costs shall be borne pursuant to sec. 91 et seq. Civil
     Procedure Code (ZPO). 

3.2  The Rent shall be due and payable in equal quarterly installments in
     arrears on January 10, April 10, July 10 and October 10 of each year
     (the"Rent Payment Dates").


<PAGE>

                                        6



3.3  Payments are to be made to a bank account named by Behringwerke in time to
     be received at the respective Rent Payment Date. Late payment shall bear
     interest at a rate of three percentage points above the relevant discount
     rate of the German Federal Bundesbank.

ARTICLE 4 - ANCILLARY COSTS

4.1  In addition to the Rent VuCo GmbH & Co. shall bear certain ancillary costs.
     Behringwerke AG shall use it best efforts to attribute the ancillary costs
     as to the various buildings and to the various tenants. Only insofar as the
     ancillary costs can not be attributed to specific buildings and/or specific
     tenants the ancillary costs shall be allocated to all tenants, where
     appropriate, on the basis of squarmeters rented, or on such other criteria
     which is reasonable for the allocation of those costs among the various
     users. Costs having been considered in calculating any fee under the Master
     Service Agreement shall not be escalated to VuCo GmbH & Co. Ancillary costs
     are:

     4.1.1     expenses of cleaning, lightning, repairing, renewing, decorating,
               maintaining and rebuilding any walls, fences, gutters, drains,
               road ways, pavements, access ways, service areas and any other
               common areas of the Premises which are or may be used or enjoyed
               by VuCo GmbH & Co. in common with any other person or persons;

     4.1.2     any insurance premiums payable by Behringwerke for insuring the
               Premises or any part thereof; 

     4.1.3     all running expenses as defined in Appendix 3 to Section 27,
               subsection 1, of the second computation order (Anlage 3 zu
               Section 27 Abs. 1 der zweiten Berechnungsverordnung).

4.2  To the extent it is not possible for legal or factual reasons that VuCo
     GmbH & Co. pay such costs and expenses directly and in its own name, VuCo
     GmbH & Co. will reimburse to Behringwerke such costs at the respective due
     date.

4.3  The costs referred to in Art. 4.1 shall be invoiced by the end of February
     of each year, at the latest, for the respective preceding year.

     VuCo GmbH & Co. shall make quarterly down-payments regarding the costs
     referred to in Art. 4.1 amounting to one quarter of the budgeted ancillary
     costs for this year. Any difference between the down-payments for a
     calendar year and the respective invoice shall 


<PAGE>

                                        7


     be settled between the parties by a single payment payable one month after
     receipt of the annual invoice pursuant to this Art. 4.3.  

4.4  Behringwerke shall adjust the quarterly down-payment in its reasonable
     discretion in accordance with Section 315 BGB if circumstances affecting
     such payments should change. This adjusted down-payment shall become
     payable as of the Rent Payment Date following receipt of the relevant
     written notice.

ARTICLE 5 - VALUE ADDED TAX

All amounts owed hereunder are net, i.e. without Value Added Tax (VAT;
UMSATZSTEUER). If a payment is subject to VAT, such tax shall be paid in
addition against presentation of an invoice in accordance with the requirements
pursuant to Section 14 VAT Act (Section 14 UMSATZSTEUERGESETZ).

ARTICLE 6 - LIABILITY, ENCUMBRANCES, RESPONSIBILITY

From the Closing Date VuCo GmbH & Co. shall be responsible for the safe
condition of the Premises including VuCo GmbH & Co.'s equipment and attachments,
whether internal or external, and for the safe operation of the Business.
Furthermore, VuCo GmbH & Co. shall fully comply with all applicable laws,
regulations, rules, ordinances and requirements, including environmental laws,
of any governmental authority having jurisdiction over the Premises or the
Business.

ARTICLE 7 - INSURANCE

7.1  Notwithstanding any other provision of this Agreement, insurance with
     respect to the Premises shall be maintained to the extent reasonable as
     follows:

     7.1.1     Behringwerke agrees to purchase, maintain and keep in force
               during the term of this Agreement, insurance against damage or
               destruction as result of risks as are for the time being
               reasonably required to be covered such as fire, lightning,
               explosion, riot, civil commotion, acts of terrorism, aircraft and
               other aerial devices or articles dropped therefrom (other than
               war risks), storm, flood and burst pipes in a sum equal to the
               full reinstatement costs of the Premises and fixtures, equipment
               and personal property contained therein, including the costs of
               demolition, shoring up and site clearance and all architect's,
               surveyor's and other professional fees and incidental expenses in
               connection with reinstatement and business interruption insurance
               covering the Premises. Such policies shall (i) name VuCo GmbH &
               Co. as an additional insured and, with respect to business
               interruption insurance, as a loss 


<PAGE>

                                        8


               payee, and (ii) provide that said insurances shall not be
               cancelled unless 30 (thirty) day's prior written notice shall
               have been given to VuCo GmbH & Co.

     7.1.2     VuCo GmbH & Co. agrees to purchase, maintain and keep in force
               during the term of this Agreement, a comprehensive general
               liability insurance policy and such further insurance or
               insurances which are necessary in respect of the Business. Such
               policies shall (i) name Behringwerke as an additional insured,
               and (ii) provide that said insurances shall not be cancelled
               unless thirty (30) days' prior written notice shall have been
               given to Behringwerke. For purposes of any general liability
               claims made in respect of the Premises, VuCo GmbH & Co.'s
               comprehensive general liability policy will be primary, and
               Behringwerke's will be secondary.

7.2  Upon request, each party shall deliver to the other certificates evidencing
     insurance coverage upon the Closing Date and upon each renewal of said
     insurances.

7.3  VuCo GmbH & Co. and Behringwerke each agree that to the extent reasonably
     possible the respective insurance carried by it against loss or damage by
     fire or other casualty shall contain a clause whereby the insurer waives
     its rights of recourse against the other party.

     Pursuant to the foregoing, Behringwerke and VuCo GmbH & Co. hereby waive
     all claims for recovery from the other party for any loss or damage to any
     of its property insured under valid and collectible insurance policies to
     the extent of any recovery collectible under such insurance. The foregoing
     waiver shall be in force only if such VuCo GmbH & Co.'s and Behringwerke's
     insurance policies contain a clause providing that such waiver shall not
     invalidate the insurance.

7.4  If either Party fails to comply with its obligation to insure then, without
     prejudice to its other remedies, the other party may effect and maintain
     the relevant insurance and the premium and other costs of so doing
     (including without limitation the cost of obtaining any insurance
     valuations) shall be paid by the party failing to take such insurance.

ARTICLE 8 - USE OF PREMISES

8.1  VuCo GmbH & Co. shall only use the Premises or any part thereof in
     accordance with the terms of this Agreement and like a diligent businessman
     in the pharmaceutical business and shall comply with all legal requirements
     and authorizations and security guidelines of Behringwerke. 

8.2  VuCo GmbH & Co. shall not do anything that would unreasonably impair or
     interfere with or tend to impair or interfere with any activities of
     Behringwerke or any other party on the Marburg sites. VuCo GmbH & Co. shall
     install at VuCo GmbH & Co.'s expense all equipment, safety 


<PAGE>

                                        9


     device, pollution control systems or other installations required at any
     time with regard to the Business. The foregoing shall apply MUTATIS
     MUTANDIS to Berhingwerke. Further Behringwerke shall use its best efforts
     that no unreasonable impairment of or interference with the Business is
     caused by other tenants of the Behringwerke site in Marburg.

8.3  Behringwerke warrants that as of the date hereof applicable zoning and land
     use law permits the use of the Premises as described in Art. 1.2. VuCo
     GmbH & Co. is responsible to maintain in place all permits required by law,
     regulation, ordinance or other requirement of any governmental authority
     with respect to the operation of the Business, except to the extent that
     only Behringwerke may obtain such permits or to the extent that such
     permits are required for common areas or entire buildings in which VuCo
     GmbH & Co.'s portion of the Premises is less than 100%, in which event
     Behringwerke must obtain such permits. The costs for such permits shall be
     apportioned between the users of these buildings equal to their portion of
     the area (FLACHENANTEIL) of the buildings.

8.4  VuCo GmbH & Co. shall not make any material alterations, improvements, or
     additions of or to the Premises (collectively the "Alteration") without
     first submitting to Behringwerke plans and specifications therefor and
     obtain Behringwerke's prior written consent in each and every instance,
     which consent shall not be unreasonably withheld or delayed. All
     alterations made by VuCo GmbH & Co. shall be at the expense and the sole
     risk of VuCo GmbH & Co. 

8.5  Before installing any heavy objects, VuCo GmbH & Co. shall ascertain from
     Behringwerke the bearing capacity of the floors. The authorized bearing
     capacity (in absolute terms and per square meter) may not be exceeded,
     otherwise VuCo GmbH & Co. shall be liable for all damage caused thereby and
     shall reimburse Behringwerke in respect of any claims resulting therefrom.

8.6  Appliances and installations may only be connected to the existing mains,
     and operated, in accordance with the mains' capacity. No interferences must
     be caused by such appliances and installations. VuCo GmbH & Co. shall
     inform itself about the capacity not be exceeded. VuCo GmbH & Co. shall
     bear the cost of any alterations or new installations of the mains or other
     supply or disposal pipes necessary due to VuCo GmbH & Co.'s operations.
     Behringwerke, however, assures to its best knowledge that the mains in
     place are sufficient for the Business as currently conducted. 


<PAGE>

                                       10


ARTICLE 9 - MAINTENANCE AND REPAIRS

9.1  VuCo GmbH & Co. is responsible for proper servicing, maintenance and repair
     of the Premises and shall maintain the Premises in good order and repair,
     as required by law, necessary to ensure the safety and health of all
     persons on the Premises.

9.2  Behringwerke is responsible for repairs of all common areas and of such
     parts of buildings which, while not being part of the Premises, are
     necessary for the Premises being used in accordance with the terms of this
     Agreement. Further all necessary works and repairs which have to be
     capitalized shall be performed by Behringwerke.  

9.3  VuCo GmbH & Co. shall only be excused of its obligation to pay rent if
     Behringwerke, having been requested by VuCo GmbH & Co. in writing with
     reasonable notice to do so, has not met its obligation under Art. 9.2 and
     such failure renders the affected portion of the Premises unusable for 5
     (five) consecutive days. After such 5 (five) day period VuCo GmbH & Co.
     will not be obligated to pay rent for such portion until such time as such
     portion is repaired and returned to usable condition in compliance with all
     relevant laws, regulations and administrative orders.

ARTCLE 10 - DESTRUCTION OF PREMISES

10.1 If the Premises or any part thereof are severely damaged or destroyed to an
     extent that repair is likely to create costs in excess of 40 % of its
     current partial value (TEILWERT) ("Damaged Property"), VuCo GmbH & Co.
     shall give immediate notice thereof to Behringwerke and shall enable
     Behringwerke to immediately assess the damages.

10.2 If Behringwerke determines, following its assessment of the damage which
     has occurred, that the Damaged Property cannot be repaired or
     reconstructed, as the case may be, within a reasonable period or with
     reasonable efforts and expenses (in either circumstance, the "Loss Event")
     the parties shall use their best efforts to agree on an adequate solution
     acceptable to both parties. If the parties fail to agree within two months
     of the Loss Event Behringwerke may elect not to repair or reconstruct the
     Damaged Property and may thereupon terminate this Agreement with regard to
     the respective part of the Premises delivering to VuCo GmbH & Co. notice
     of such election.  In such event, the rent shall be reduced
     proportionately. VuCo GmbH & Co. can terminate the lease if the remaining
     Premises are insufficient for the Business and Behringwerke cannot provide
     for a reasonable alternative. In case the Damaged Property is not repaired
     or reconstructed, Behringwerke shall be entitled to all payments made by
     insurers with respect to the Damaged Property.


<PAGE>

                                       11

ARTICLE 11 - STRUCTURAL CHANGES BY BEHRINGWERKE


11.1 Behringwerke may, even without VuCo GmbH & Co.'s consent, carry out any
     improvements or structural changes necessary or expedient to maintain,
     preserve, modernize or expand the Premises, to eliminate imminent danger,
     or to repair defects. In such case, Behringwerke shall reasonably take into
     account the interests of VuCo GmbH & Co. VuCo GmbH & Co. shall allow
     Behringwerke reasonable access to the Premises at reasonable times and
     shall not obstruct or delay the execution of the work.

11.2 VuCo GmbH & Co. shall only be entitled to make claims against Behringwerke
     because of any work carried out pursuant to Art. 11.1 if VuCo GmbH & Co.'s
     activities have been considerably impaired thereby for more than 5 (five)
     consecutive days. 

ARTICLE 12 - ASSIGNMENT AND SUBLETTING

12.1 VuCo GmbH & Co. is only entitled to assign or transfer all or any of its
     rights, benefits and obligations under this Agreement to affiliates (as
     defined in sec. 15 et seq. Stock Corporation Act - AKTIENGESETZ) of Chiron
     Corporation. Any other assignment or sublet needs the prior written consent
     of Behringwerke which consent shall not be unreasonably withheld.
     Behringwerke is only entitled to assign all or any of its rights, benefits
     and obligations under this Agreement to affiliates (as defined in Sec. 15
     et.seq. Stock Corporation Act - AKTIENGESETZ) of Hoechst AG. Any other
     assignment by Behringwerke needs the prior written consent of VuCo GmbH &
     Co. which consent shall not be unreasonably withheld.

12.2 In the event of subtenancy, VuCo GmbH & Co. shall be absolutely liable for
     all acts and omissions of the sub-tenant.

12.3 In the event of subtenancy, VuCo GmbH & Co. hereby and as of now assigns to
     Behringwerke as security all claims, including any accompanying liens which
     it may have against the sub-tenant.

ARTICLE 13 - CHANGE OF LEGAL ENTITY, SALE OF BUSINESS

13.1 VuCo GmbH & Co. must notify Behringwerke immediately of any change in
     control of VuCo GmbH & Co. or of its intention to sell or close the
     Business or any material part thereof.

13.2 In case of the sale of VuCo GmbH & Co.'s business or a part thereof, buyer
     has no claim to have this Agreement assigned to him.


<PAGE>

                                       12


ARTICLE 14 - SIGNS

     Subject to all applicable zoning or regulatory requirements, VuCo GmbH &
     Co. may install at its own expense and after obtaining any necessary
     permits and Behringwerke's approval (which shall not be unreasonably
     withheld) appropriate monument signs at the entrance to the Premises which
     in any event may be comparable in number, size and overall impact to the
     monuments of Behringwerke in the same or similar locations and appropriate
     additional exterior signs on the buildings; provided, however, that upon
     termination of this Agreement VuCo GmbH & Co. shall remove said sign(s) and
     repair damages caused thereby. 

ARTICLE 15 - INDEMNIFICATION

15.1 VuCo GmbH & Co. will indemnify, defend and hold Behringwerke and its
     shareholders, subsidiaries, affiliates, officers, directors, agents and
     employees harmless from and against any claims, costs, liabilities, fines,
     damages or expenses (including reasonable attorney's fees) arising from or
     alleged to arise from or out of VuCo GmbH & Co.'s operations or from or out
     of an act, omission, fault, negligence or other misconduct of VuCo GmbH &
     Co., its agents, ser-vants, employees, visitors or contractors with or at
     the areas of the Premises over which VuCo GmbH & Co. has control occurring
     after the Closing Date, except arising out of Behringwerke's gross
     negligence.

15.2 Behringwerke will indemnify, defend and hold VuCo GmbH & Co. and its
     general and limited partners, subsidiaries, affiliates, officers,
     directors, agents and employees harmless from and against any claims,
     costs, liabilities, fines, damages or expenses (including reasonable
     attorney's fees) arising from or alleged to arise from or out of
     Behringwerke's operations or from or out of an act, omission, fault,
     negligence or other misconduct of Behringwerke, its agents, servants,
     employees, visitors or contractors on the Premises or the Marburg sites,
     except arising out of VuCo GmbH & Co.'s gross negligence.

15.3 To the extent the mutual obligations pursuant to Art. 15.1 and 15.2 exceed
     the statutory liability, such obligations shall apply only if approved by
     the respective insurance companies.

15.4 Neither Party shall be responsible for consequential damage hereunder.

ARTICLE 16 - DEFAULT, TERMINATION

16.1 The statutory provisions, except Section 554 German Civil Code (Section 554
     BGB), shall apply for the termination of the Lease for serious cause.


<PAGE>

                                       13



16.2 Behringwerke may terminate the Lease without notice in particular if one or
     more of the following events of default occur during the term of this
     Agreement:

     16.2.1    VuCo GmbH & Co. fails to pay any regular instalment of Rent
               and/or ancillary costs when due and such default continues for 15
               (fifteen) days upon receipt of a written notice from
               Behringwerke, provided Behringwerke needs not furnish more than 2
               (two) such notices in any calendar year; or

     16.2.2    VuCo GmbH & Co. defaults in the performance of any other
               requirement, obligation or covenant of this Agreement and any
               such failure continues for 30 (thirty) days after notice thereof
               from Behringwerke (excepting, however, any default which is not
               reasonably susceptible of cure within said period of 30 (thirty)
               days and which VuCo GmbH & Co. shall in good faith and with due
               diligence be proceeding to cure); or

     16.2.3    bankruptcy or composition proceedings are instituted against VuCo
               GmbH & Co. or if a petition in bankruptcy filed by VuCo GmbH &
               Co. is dismissed for lack of assets; or

     16.2.4    the interest of VuCo GmbH & Co. in the Premises is taken upon
               execution or by other process of law directed against VuCo GmbH &
               Co., or taken upon or subjected to any attachment by any creditor
               of VuCo GmbH & Co. or claimant against VuCo GmbH & Co., and such
               attachment is not discharged within 15 (fifteen) days.

16.3 VuCo GmbH & Co. may also terminate the Lease if the Business cannot be
     operated on the Premises due to public law; provided that VuCo GmbH & Co.
     shall use reasonable efforts to avoid the applicability of such law,
     including obtaining a waiver.

16.4 VuCo GmbH & Co. hereby grants to Behringwerke full and free right to enter
     into and upon the Premises in such event as permitted by law, to repossess
     the Premises and to remove objects belonging to VuCo GmbH & Co.

16.5 Any and all objects in the possession of VuCo GmbH & Co. at termination of
     the lease (irrespective of ownership) or to which VuCo GmbH & Co. has a
     claim, may be removed and/or stored at the discretion of Behringwerke at
     the risk, cost and expense of VuCo GmbH & Co. VuCo GmbH & Co. shall pay to
     Behringwerke, upon demand any and all expenses incurred in such removal and
     all storage charged against such property so long as the same shall be in
     Behringwerke's possession or control. Any such objects not retaken by VuCo
     GmbH & Co. from storage within 40 (forty) days after removal from the
     Premises may be sold (VERWERTET) by 


<PAGE>

                                       14



     Behringwerke without restrictions. The proceeds less any and all costs and
     claims by Behringwerke shall be paid to VuCo GmbH & Co.

16.6 On termination of the Lease, whether in accordance with this Art. 16 or
     Art. 2 of this Agreement, VuCo GmbH & Co. shall immediately surrender the
     Premises, and deliver possession thereof to Behringwerke, properly
     renovated and repaired. This shall include: all repairs pursuant to
     Art. 10.1, renewal of the floor coverings and wall paper, painting of
     radiators and heating pipes, as well as of doors, window frames and door
     frames, all at least to the standard as of the Closing Date. Should VuCo
     GmbH & Co. surrender the Premises without having carried out the work
     described above, Behringwerke may carry out all necessary work at VuCo
     GmbH & Co.'s expense. Behringwerke's claim in respect of the costs thereby
     incurred shall also subsist if these works are carried out by the
     subsequent tenant.

ARTICLE 17 - HAZARDOUS MATERIALS

17.1 Hazardous materials or material to be monitored (UBERWACHUNGSBEDURFTIG) or
     waste as defined by the applicable laws, regulations and administrative
     orders relating to chemicals, hazardous materials and waste (CHEMIKALIEN-,
     GEFAHRSTOFF- UND ABFALLRECHT) may only be stored, handled, treated,
     disposed of, discharged, produced, processed or used by VuCo GmbH & Co.
     anywhere in or on the Premises or the common areas with the prior written
     consent of Behringwerke and in full compliance with all applicable laws,
     regulations and administrative orders. Such consent shall not unreasonably
     be withheld. Such consent of Behringwerke is not required for the use of
     such hazardous materials or material to be monitored or waste as are
     currently in use or being created on the Premises. VuCo GmbH & Co. shall
     keep and maintain updated material safety data sheets (or similar documents
     required by law) and shall make them available for Behringwerke's
     inspection upon request.

17.2 Each of Behringwerke and VuCo GmbH & Co. shall (i) promptly notify the
     other of any complaints, notice or other correspondence received from any
     third party concerning any actual or alleged violation of any applicable
     law, regulation or administrative order regarding hazardous materials,
     material to be monitored or waste; (ii) promptly notify the appropriate
     public body in case of any emission, release, leakage or emergency of any
     kind (STORFALL).

17.3 VuCo GmbH & Co.'s responsibilities, covenants and liabilities under this
     Art. 17 shall survive the expiration or earlier termination of this
     Agreement. Any events arising from acts or omissions occurring prior to the
     Closing Date are the responsibility of Behringwerke.


<PAGE>

                                       15


ARTICLE 18 - FORCE MAJEURE

     Neither party shall be responsible for delays or inability to perform its
     obligations hereunder due to force majeure or for other causes beyond the
     reasonable control of such party including acts of other tenants,
     governmental restriction, regulation or control, labor dispute, accident,
     mechanical breakdown, shortages or inability to obtain labor, fuel, steam,
     water, electricity or materials, acts of God, enemy action, civil commotion
     or fire or other casualties.

ARTICLE 19 - CONFIDENTIALITY

19.1 Any information whether written, oral or otherwise provided by a party to
     the other party and any information obtained by a party in connection with
     this Agreement, including the terms and conditions of this Agreement, shall
     be treated as confidential by the party receiving such information, shall
     only be used for purposes consistent with this Agreement and shall not be
     disclosed to any third party unless the party who provided such information
     has given its prior written consent to such other use or disclosure;
     provided, however, that each party may disclose such information for
     purposes consistent with this Agreement to its employees, agents and sub-
     contractors, if such employee, agent or sub-contractor agrees to keep such
     information confidential as if it were a party hereto.

19.2 The obligations of confidentiality, including the obligations of restricted
     use, shall continue for a period of ten years after the termination of this
     Agreement. 

19.3 Excluded from the restrictions provided in Art. 19.1 and 19.2 above is all
     information that has been disclosed by one party to the other party and
     which is:

     19.3.1    information that such other party possessed in its own right
               before disclosure by the first party;

     19.3.2    information that is in the public domain at the time of
               disclosure by a party or has become part of the public domain
               through no fault of the other party having received such
               information;

     19.3.3    information that such other party has received, without
               restriction on its disclosure, legitimately from a third party
               not deriving the same from the party who made the original
               disclosure.

19.4 Information which must be disclosed in order to comply with any laws,
     regulations or administrative or court orders may only be disclosed to the
     entities named in such laws, 


<PAGE>

                                       16


     regulations or orders. Prior to such disclosure, the other party must be
     informed about the nature, extent and contents of the information to be
     disclosed.

ARTICLE 20 - LAW; VENUE

This Agreement shall be governed by, and construed in accordance with, the law
of the Federal Republic of Germany. The arbitration clause in the Contribution
Agreement shall not be applied.

ARTICLE 21 - FINAL PROVISIONS

21.1 Behringwerke, his agents or representatives shall, upon giving prior
     notice, be entitled to inspect the Premises during VuCo GmbH & Co.'s normal
     business hours and at reasonable intervals. In the event of a release or
     other environmental emergency or any other emergency at the Premises
     Behringwerke shall have the right to enter the Premises for purposes of
     responding to such release or emergency at any time without giving VuCo
     GmbH & Co. notice in advance.

21.2 The access to the Premises shall be governed by Art. 11 of the Master
     Service Agreement.

21.3 VuCo GmbH & Co. may only set-off (AUFRECHNUNG), and exercise rights of
     retention (ZURUCKBEHALTUNG), regarding claims against the rent or ancillary
     costs if these claims are undisputed between the parties or acknowledged by
     Behringwerke or confirmed by a non-appealable decision.

21.4 Any amendment, cancellation or supplement of a provision of this Agreement,
     including this Art. 21.4 and any notification under this Agreement must be
     in writing in order to be valid, unless more stringent requirements as to
     the form are stipulated by the applicable law.

21.5 This Agreement embodies the entire agreement between the parties hereto
     with regard to the subject matter hereof and there have been no agreements,
     representations or warranties between the parties with regard to the
     subject matter hereof other than those set forth or provided for herein.

21.6 The Annexes hereto are integral parts of this Agreement, and all references
     herein to this "Agreement" shall also include the Annexes.

21.7 If any provision of this Agreement is held to be prohibited by or invalid,
     such provision will be ineffective only to the extent of such prohibition
     or invalidity, without invalidating the remainder of such provision or the
     remaining provisions of this Agreement. To the extent that a provision is


<PAGE>

                                       17


     ineffective or invalid, it shall be replaced by an effective and valid
     provision which comes as close as possible to the economic purpose of the
     ineffective or invalid provision.

__________, this ___ day of __________, 1996


BEHRINGWERKE AG                         [VuCo GmbH & Co.]

______________________________          ______________________________
By:                                     By:
Title:                                  Title:


<PAGE>

Annex 1.1.(a) to Lease Agreement


<TABLE>
<CAPTION>

------------------------------------------------------------------------------
                                               Usage by Vaccine Unit
                                   -------------------------------------------
                                                                           2
Building                              %                                   m
------------------------------------------------------------------------------

<S>                                <C>                                    <C>
H 6                                 19,5                                   663
------------------------------------------------------------------------------
H 10                                30,0                                  1058
------------------------------------------------------------------------------
H 12                                61,0                                  2312
------------------------------------------------------------------------------
H 15                                51,0                                     ?
------------------------------------------------------------------------------
Z 20                                 6,0                                    33
------------------------------------------------------------------------------
Z 21                                40,0                                   690
------------------------------------------------------------------------------
Z 25                                 6,2                                   404
------------------------------------------------------------------------------
Z 26/30                             19,9                                  1287
------------------------------------------------------------------------------
H 33                                49,9                                  1205
------------------------------------------------------------------------------
H 38                                25,8                                    66
------------------------------------------------------------------------------
M 544                               10,0                                    49
------------------------------------------------------------------------------
H 70                                 0,3                                     ?
------------------------------------------------------------------------------
H 11                                75,0                                  1734
------------------------------------------------------------------------------
H 21                                50,0                                  2727
------------------------------------------------------------------------------
H 26                               100,0                                  1565
------------------------------------------------------------------------------
H 28                                75,0                                  5400
------------------------------------------------------------------------------
H 32                                66,0                                   515
------------------------------------------------------------------------------
H 34                                80,0                                   317
------------------------------------------------------------------------------
M 218                               40,0                                   592
------------------------------------------------------------------------------
M 537                              100,0                                  1440
------------------------------------------------------------------------------
</TABLE>


<PAGE>

                                              ANNEX 1.4 (b)
                                  TO THE PURCHASE AGREEMENT


                          PARTNERSHIP AGREEMENT
                                   OF
                  CHIRON BEHRING BIOCINE GmbH & CO. KG
                 (FORMER: BEHRING VAKZINE GmbH & CO. KG)

                                 BETWEEN
                             BEHRINGWERKE AG
                                   AND
        32.  CORSA VERWALTUNGSGESELLSCHAFT mbH ("32.CORSA GmbH")
                                   AND
        31.  CORSA VERWALTUNGSGESELLSCHAFT mbH ("31.CORSA GmbH")


In consideration of the Purchase and Assignment Agreement between
Behringwerke AG and 31. Corsa GmbH (the "Purchase Agreement"), the
Contribution Agreement between Behring Vakzine GmbH & Co KG and Behringwerke
AG and the Shareholders' Agreement between Behringwerke and 3 1. Corsa GmbH.
the Parties to this Agreement agree to the following terms of their
partnership:


  1.  NAME, REGISTERED OFFICE

      1.1   The name of the Partnership shall be

                  CHIRON BEHRING BIOCINE GmbH & CO. KG

      1.2   The Partnership has its registered office in Marburg.



  2.  PURPOSE OF THE PARTNERSHIP

      2.1   The purpose of the Partnership is the development, production and
            distribution of pharmaceutical products, in particular human
            vaccines.

<PAGE>
                                     2


      2.2   The Partnership is entitled to take all actions which are necessary
            or appropriate to further the purpose of the Partnership directly or
            indirectly.

      2.3   The Partnership is entitled to establish other enterprises and
            branches within Germany and other countries or to acquire other
            business enterprises, including partnerships, thereon.


  3.  PARTNERS; PARTNERSHIP CAPITAL

      3.1   The General Partner is 32.Corsa GmbH.  The General Partner does not
            make a capital contribution and does not participate in the capital
            of the Partnership.

      3.2   The Limited Partners of the partnership are

            3.2.1     Behringwerke AG with a partnership interest of 51%

            3.2.2     31. Corsa GmbH with a partnership interest of 49%.


      3.3   The capital of the Partnership has been or will be contributed in
            kind by Behringwerke AG pursuant to be Contribution
            Agreement prior to the transfer of the 49% interest in the 
            Partnership pursuant to the Purchase Agreement. The capital 
            contribution of Behringwerke under the Contribution Agreement is 
            fixed and may not be withdrawn.

      3.4   The capital contribution of the Limited Partners to be registered in
            the commercial register (Hafteinlage) shall be:

            3.4.1     Behringwerke AG DM 2,550,000 (in words: Deutsche
                      Mark two million five hundred fifty thousand)

            3.4.2     31. Corsa GmbH DM 2,450,000 (in words: Deutsche
                      Mark two million four hundred fifty thousand)


<PAGE>

                                    3



      3.5   The capital accounts I and II determine the interest of each of the
            Partners in the Partnership ("Partnership Interest").


  4.  PARTNER ACCOUNTS

      4.1   For each partner,a capital account I, a capital account II, a
            reserve account, a loss carry forward account and a transaction
            account shall be maintained.

      4.2   The contribution to be registered in the commercial register
            shall be booked into the capital account I of each of the Limited
            Partners.  This capital account is fixed.  Pursuant to the
            Contribution Agreement Behringwerke has contributed DM 5,000,000
            (in words: Deutsche Mark five million) in kind to the capital
            account I of Behringwerke, of which 49 % will be transferred to
            the capital account I of 31. Corsa GmbH.

      4.3   The remainder of the capital contribution of Behringwerke in
            accordance with the Contribution Agreement shall be booked into
            the capital account II of Behringwerke.

            4.3.1     49 % of such capital is transferred according to the
                      Purchase Agreement to the capital account II of 31.
                      Corsa GmbH.

            4.3.2     Any future contribution of Behringwerke to the
                      Partnership pursuant to the Contribution Agreement will
                      be booked at 51% into the capital account II of
                      Behringwerke and at 49% into the capital account II of
                      31. Corsa GmbH.

            4.3.3     The contributions to the capital accounts II are fixed
                      and may not be withdrawn by either Partner.

      4.4   Profits of the Partnership which are not distributed are booked
            into the reserve account of each Partner in proportion to their
            Partnership Interest.

      4.5   Losses attributable to each Partner shall be booked into the
            loss-carry-forward account of each Partner in proportion to their
            Partnership Interest.

<PAGE>
                                     4



      4.6   Distributable profit shares, withdrawals, compensation for
            services rendered, commissions, other than commissions pursuant
            to clause 4.7 of the Purchase Agreement, which shall be paid to
            Behringwerke in accordance with the Purchase Agreement,
            reimbursement of expenses, interest and all other payments
            between the Partnership and the Partners shall be booked into the
            respective transaction accounts.

      4.7   In addition, separate loan accounts shall be kept to the extent
            Partners grant loans to the Partnership.

      4.8   The capital accounts I and II, the reserve accounts and the
            transaction account shall not bear interest.  Debit and credit 
            balances of loan accounts, if any, shall bear interest at the rate 
            specified in the relevant loan agreement, if any, or at due year 
            FIBOR.


  5.  FISCAL YEAR, ANNUAL FINANCIAL STATEMENTS; INDEMNIFICATION

      5.1   The fiscal year runs from January 1 of each year to December 31.

      5.2   Within two months after the end of each fiscal year,the General
            Partner shall prepare the annual financial statements (annual
            balance sheet and profit and loss statements) for the preceding
            fiscal year and shall promptly submit and explain the annual
            financial statements to the Advisory Board members and to the
            appointed auditors for the purpose of examination.

      5.3   With respect to the structure (Gliederung) and evaluation
            (Bewertung), the financial statements shall comply with such
            applicable for corporations (Kapitalgesellschaften) pursuant to
            German generally accepted accounting principles ("GAAP"), a
            supplement (Anhang) and situation report (Lagebericht) are not
            necessary.  As a matter of principle, the financial statements
            must comply with the applicable provisions of profit
            determination pursuant to German Income Tax Law
            (einkommensteuerliche Gewinnermittlung), unless compulsory
            commercial law provisions, this Partnership Agreement, or
            partnership resolutions provide otherwise.

            To the extent that assessments by the tax authorities require a
            revision of the financial statements, only such revised financial
            statements shall govern rights

<PAGE>
                                     5



      5.4   To the extent that assessments by the tax authorities require a
            revision of the financial statements, only such revised financial
            statements shall govern rights and duties of the parties
            hereunder.  To the extent that such tax assessment requires a
            revision of the financial statements for several years, it is for
            internal purposes sufficient to amend the last financial
            statement.  The distribution of profits pursuant to clause 6.2
            shall be adapted for all financial statements subject to such
            revision.

      5.5   The financial statements shall be audited.  Auditor may only be
            an internationally recognized Wirtschaftsprufungsgesellschaft
            acceptable to all parties hereof.

      5.6   Upon approval of the financial statements by the Advisory Board
            and the Partners' Meeting, they shall be signed by the
            Geschaftsfuhrer of the General Partner.

      5.7   The annual financial statements shall also be prepared in
            accordance with U.S. GAAP.


      5.8   Each Limited Partner may also, without approval of the General
            Partner, exercise  information rights and controlling rights
            pursuant to sects. 118, 166 Commercial Law (HGB) whereby
            each Limited Partner can exercise such rights through a third
            person who  is bound by a professional confidentiality
            obligation.


  6.  Distribution of Profits and Losses

      6.1   The Partners shall share in the profits and losses as calculated
            after deduction of the expenses of the General Partner and of any
            compensation otherwise due to the Partners in the ratio of their
            Partnership Interests.  Regardless of the consummation of any
            transfer of the 51% Partnership Interest from Behringwerke AG to
            31.  Corsa GmbH pursuant to the Purchase Agreement (i.e.,
            exercise of Chiron Call Option or Behring Put Option), 31. Corsa
            GmbH shall at any time indemnify Behringwerke AG for any tax
            obligations relating to tax periods after the Closing Date of
            Behringwerke AG stemming from its Partnership Interest unless
            covered by clause 6.2; the indemnification

<PAGE>

                                     6





            is limited to tax claims relating to trade tax and value added
            tax but shall in no way include capital gain tax.

      6.2   Profit shares necessary to balance withdrawals of Partners for
            tax payments shall be booked on the transaction account.  The
            remainder of the profits shall be booked into the reserve
            accounts or the loss carry forward accounts as appropriate,
            unless the Partners unanimously provide otherwise.

      6.3   As long as a loss carry forward exists in the loss carry forward
            accounts, it shall be compensated by subsequent profits.  Only
            thereafter may any profit shares be booked into the transaction
            account or the reserve accounts.


  7.  WITHDRAWALS

      7.1   Each Partner may request withdrawals only from credit balances on
            its transaction account.

      7.2   Any withdrawals in excess thereof shall require a resolution by
            the Partners.


  8.  MANAGEMENT, REPRESENTATION

      8.1   The General Partner shall solely be entitled and shall have the
            sole responsibility to manage and represent the Partnership.

            The General Partner shall obtain the Advisory Board's approval
            for all business decisions which are of material importance to
            the Partnership, including, but not limited to, approval of the
            annual budget and the following matters:

            8.1.1     sale or acquisition of a company, parts of a company,
                      business (Betriebe) or parts of a business
                      (Betriebsteile) or entering into, or termination of
                      company lease agreements (Betriebspachtvertrage):

            8.1.2     sale, acquisition or encumbrance of controlling
                      interests in any other company or business:

<PAGE>
                                     7




            8.1.3     taking up new area of business and activities or
                      cessation of existing areas of business and activities;

            8.1.4     entering into, amendment and termination of enterprise
                      contracts (Unternehmensvertrage);

            8.1.5     acquisition, sale and transfer, encumbrance and pledge
                      of fixed assets, including real property, buildings and
                      rights of real property nature (if the transaction
                      value in each individual case is in excess of DM
                      500,000 (in words: Deutsche Mark five hundred
                      thousand);

            8.1.6     entering into or amending any contract with a value of
                      more than DM 500,000 (in words: Deutsche Mark five
                      hundred thousand);

            8.1.7     taking up and granting of loans and credits,
                      assumptions of guarantees, strict guarantees and other
                      liabilities of similar nature if the transaction value
                      in each case is in excess of DM 500,000 (in words:
                      Deutsche Mark five hundred thousand);

      8.2   The approval of the Advisory Board to be obtained pursuant to the
            foregoing may also be made in form of a general authorization for
            particular types of the aforementioned transactions and matters.
            Any such general authorization must precisely describe the
            transactions and matters in question as well as the purpose and
            the time frame in which they must be completed.


  9.  ADVISORY BOARD

      9.1   The Partnership shall have an Advisory Board.  The Advisory Board
            shall be composed of four (4) members.  Each Limited Partner
            shall appoint two members (including one senior member).

      9.2   The Advisory Board shall advise the management and shall consider
            for approval the consents required according to clause 8.

<PAGE>

                                    8

      9.3   The Advisory Board shall resolve its decision with a simple
            majority of its votes.  In the event that a majority decision
            cannot be reached, the following special procedures shall be used
            to break a deadlock:

            9.3.1     the senior Advisory Board member appointed by 
                      Behringwerke, following reasonable consultation with the 
                      senior member appointed by the other party, shall have 
                      the decisive vote in matters relating to the following 
                      agreements:

            [CONFIDENTIAL TREATMENT REQUESTED]

            9.3.2     The senior Advisory Board member appointed by Chiron, 
                      following reasonable consultation with the senior member 
                      appointed by the other party, shall have the decisive 
                      vote in all other matters referred to the Advisory Board.

      9.4   The Advisory Board shall meet at least every 14 months or whenever 
            requested by the CEO or by any of the senior members of the Advisory
            Board.  The meetings can be held by telephone or video conference.
            Meetings shall convene with a notice period of seven (7) days if 
            not otherwise unanimously agreed.  Action can be taken by unanimous 
            written consent.  The Advisory

<PAGE>
                                      9



            Board may adopt its own internal rules of procedure to be adapted 
            from time to time.


  10. Partners' Resolutions, Partners' Meeting

      10.1  The decisions reserved to the Partners by law or by the
            Partnership Agreement regarding the affairs of the Partnership
            shall be made by resolutions of the Partners.

      10.2  Partners' resolutions shall be adopted in partners' meetings
            unless the General Partner requests that a resolution is adopted
            in writing, by telex, by telefax and no objection is raised by a
            Limited Partner.

      10.3  The partners' meeting shall be called by the General Partner in
            its own right or upon request of any Limited Partner.  The
            General Partner may join the partners' meetings unless the
            partners request otherwise.

      10.4  The partners' meeting shall have a quorum when at least 75% of
            the Limited Partnership Interest is represented.  If a properly
            convened meeting has no quorum within one (1) hour of the time
            for which it was convened, the meeting shall automatically be
            adjourned and reconvened for the same time at the same place five
            business days later.  Such reconvened meeting shall have a quorum
            if at least one Limited Partner is present.  All resolutions of
            the partners' meeting require a simple majority of the votes
            present or represented at the meeting unless a higher majority is
            required by law.

      10.5  Each DM 1,000 of the Limited Partnership is equivalent to one
            vote.

      10.6  Except as otherwise provided in this Partnership Agreement, the
            Partners may also vote in matters of their own.

      10.7  Resolutions of the Partners shall be recorded in the minutes of
            the Partners' meeting or, in case of resolutions adopted outside
            of such meetings, in separate minutes to be drawn up and to be
            signed by the General Partner.The
            Partners shall in each case receive copies of such minutes  without
            delay.
                                    10

      10.8  Partners may only challenge the validity of Partners' resolutions
            within a period of one month following adoption in a Partners'
            meeting in which they have participated, or following receipt of
            the minutes recording the Partners' resolution by filing suit.
            After expiration of the above period, any defect of a Partners'
            resolution shall be deemed cured.


  11. TRANSFER OF PARTNERSHIP INTERESTS

      The Partners agree that any transfer, assignment or encumbrance of the
      Partnership Interest or parts thereof requires the prior written
      consent of the other Partner, which shall not be unreasonably withheld,
      provide that, (i) no consent shall be required if the Limited
      Partnership interests are transferred, assigned or encumbered to, or
      for the benefit of, a wholly owned subsidiary of the respective Partner
      and which will remain such a wholly owned subsidiary of a Partner, and
      (ii) such Partner has proven to the other Partner by submission of a
      written agreement that such subsidiary has agreed to be bound by be
      terms of this Agreement and the Purchase Agreement.  For the avoidance
      of doubt: no such transfer or assignment by 31. Corsa GmbH may in any
      respect impair Behringwerke AG's rights under the Purchase Agreement in
      particular, its rights against the Guarantor for payment of the Option
      Purchase Price in case the Chiron Call Option or the Behring Put Option
      is exercised.

  12. Bankruptcy

      In the event a bankruptcy or judicial composition proceeding is opened
      with respect to the assets of a Partner, the membership of such Partner
      shall terminate as soon as the underlying court order becomes final.


  13. TERM OF THE PARTNERSHIP

      13.1  The partnership shall commence upon its being established.

<PAGE>

                                     11


      13.2  The partnership is established for an indefinite period of time;
            the partnership may be terminated for the first time with a
            written notice of 6 months to December 31, 2001.

            If any of the Partners ceases to be a member of the partnership
            and his Partnership Interest is not transferred to a successor,
            the other Partner may take over the Partnership Interest in whole
            or in part.

      13.3  In case of dissolution of the partnership, the liquidation shall
            be effected in accordance with the statutory rules by
            liquidators.  Each Limited Partner participates in the
            liquidation surplus in the ratio of his Limited Partnership
            Interest.

      13.4  Effective as of January 1, 2002, this Partnership Agreement shall
            be adjusted to reflect the German Commercial Code (HGB).

  14. WITHDRAWAL COMPENSATION

      In the event a Partner withdraws from the partnership or the
      membership of this Partner is terminated due to Sect. 12, such Partner
      shall receive a withdrawal compensation . The withdrawal compensation
      shall be the nominal amount of the Partnership Interest of the
      withdrawing partner plus the balance in his transaction account.  The
      withdrawal compensation is payable in equal installments over a period
      of five years.

  15. Compensation of General Partner

      15.1  To the extent the General Partner's business activities are
            exclusively activities in connection with or on behalf of the
            Partnership, the Partnership shall reimburse the General Partner
            for all expenses incurred therewith.


      15.2  In addition to clause 15. 1, the General Partner shall receive at
            the end of each fiscal year of the Partnership a compensation in
            the amount of 2 % of the General Partner's net equity value as of
            the beginning of such financial year.

      15.3  Any compensation paid to the General Partner shall be booked as
            cost in the profit and loss statements of the Partnership.

<PAGE>

                                    12


  16. CAPITAL INJECTION; SHAREHOLDER LOANS

      16.1  Under no circumstances Behringwerke AG is obliged to inject any
            capital into the partnership or to grant any shareholder loans.

      16.2  31. Corsa GmbH undertakes the responsibility to ensure that the
            Partnership shall have sufficient cash to meet all its
            obligations for at least a period of 6 (six) months after the
            Closing Date as defined in the Purchase Agreement.

  17. CONCLUDING PROVISIONS

      17.1  The Partners shall keep all confidential information received
            from the partnership or from the other Partners in strict
            confidence without limitation in time, even after their
            withdrawal from the partnership.

      17.2  In case individual provisions of the Partnership Agreement are or
            become invalid in whole or in part, the validity of the remaining
            provisions shall remain unaffected thereby.  The parties shall
            instead of the invalid provision agree on an appropriate valid
            provision which approximates best the intent and purpose of the
            invalid provision.

      17.3  This Partnership Agreement and its interpretation shall be
            governed by the laws of the Federal Republic of Germany.  Court
            venue shall be Marburg for all disputes among the Partners.

      17.4  31. Corsa GmbH shall hold Behringwerke free and harmless from any
            damages and shall actually conduct all relevant negotiations and
            court proceedings on behalf of Behringwerke, as a consequence of
            any withdrawals from the capital account I caused or otherwise
            initiated by 31. Corsa GmbH, including withdrawals after exercise
            of the Chiron Call Option or the Behring Put Option and shall
            hold Behringwerke free and harmless; this also applies in case of
            withdrawals necessary for the satisfaction of clause 4.7 of the
            Purchase Agreement.


<PAGE>

                                                                     ANNEX 3.4
                                                      to the Purchase Agreement



                               SHAREHOLDERS' AGREEMENT
                          For VuCo GmbH and VuCo GmbH & Co.
                          ---------------------------------



BETWEEN

Behringwerke AG
                                                               ("Behringwerke")


AND



         31. CORSA Verwaltungsgesellschaft mbH
                                                                      ("Buyer")



         (Behringwerke and the Buyer each also referred to as "Shareholder" or
         "Party")


<PAGE>

                                          2



INTRODUCTION

A.  Pursuant to the purchase and assignment agreement, of which this Agreement
    forms an annex (the "Purchase Agreement"), Behringwerke has sold to Buyer a
    49% interest in VuCo GmbH and VuCo GmbH & Co. (hereinafter collectively the
    "Companies").

B.  With regard to the exercise of Behringwerke's and the Buyer's rights as
    shareholders and partners of the Companies, the Parties wish to enter into
    this Shareholders' Agreement in order to coordinate their cooperation with
    regard to the management of the Companies.

C.  All terms defined in the Purchase Agreement shall have the same meaning in
    this Shareholders' Agreement.

In consideration hereof the parties agree as follows:

1.  STRUCTURE OF THE COMPANIES

    1.1  VuCo GmbH & Co. is organized as a limited partnership with VuCo GmbH
         as its sole general partner. VuCo GmbH & Co. will be exclusively
         managed and represented by VuCo GmbH.

    1.2  VuCo GmbH will be managed by a Chief Executive Officer
         (GESCHAFTSFUHRER).  The Chief Executive Officer shall not be bound by
         fiduciary obligations vis-a-vis any particular Shareholder other than
         those applicable vis-a-vis all Shareholders pursuant to law, the
         Articles of Association of VuCo GmbH (the "Articles"), the Partnership
         Agreement of VuCo GmbH & Co. (the "Partnership Agreement") and this
         Shareholders' Agreement.

    1.3  VuCo GmbH & Co. shall have an Advisory Board (BEIRAT).

    1.4  To the extent the Companies will be required to establish an
         AUFSICHTSRAT by matter of law, the parties hereto will pursue the
         intent of this Agreement regardless of such AUFSICHTSRAT.


<PAGE>

                                          3



2.  RULES GOVERNING THE SHAREHOLDERS' MEETINGS AND PARTNERS' MEETINGS

    2.1  The shareholders' meetings of VuCo GmbH shall be convened at regular
         intervals not exceeding 14 months and upon no less than seven (7)
         business days notice in writing, such notice to include an agenda
         specifying the matters to be resolved.

    2.2  The shareholders' meetings of VuCo GmbH shall be called in by the
         Chief Executive Officer of VuCo GmbH in its own right or upon request
         of any Shareholder.  The Chief Executive Officer may join the
         shareholders' meetings, unless any Shareholder requests otherwise.

    2.3  The shareholders' meeting shall have a quorum when at least 75 % of
         the stated capital of VuCo GmbH are represented.  If a properly
         convened meeting has no quorum within 1 (one) hour of the time for
         which it was convened, the meeting shall automatically be adjourned
         and reconvened for the same time at the same place five business days
         later.  Such reconvened meeting shall have a quorum if at least one
         Shareholder is present.  All resolutions of the shareholders' meeting
         require a simple majority of the votes, present or represented at the
         meeting, unless a higher majority is required by law.

    2.4  For the partners' meetings of VuCo GmbH & Co., the foregoing
         provisions shall apply MUTATIS MUTANDIS.


3.  PRINCIPLES OF MANAGEMENT

    3.1  The management of VuCo GmbH shall obtain the Advisory Board's approval
         for all business decisions which are of material importance to VuCo
         GmbH or VuCo GmbH & Co., including, but not limited to, approval of
         the annual budget and plan, and the following matters:

         (a)  sale or acquisition of a company, parts of a company, business
              (BETRIEBE) or parts of a business (BETRIEBSTEILE) or entering
              into, or termination of company lease agreements
              (BETRIEBSPACHTVERTRAGE);


<PAGE>

                                          4



         (b)  sale, acquisition or encumbrance of controlling interests in any
              other company or business;

         (c)  taking up new area of business and activities or cessation of
              existing areas of business and activities;

         (d)  entering into, amendment and termination of enterprise contracts
              (UNTERNEHMENSVERTRAGE);

         (e)  acquisition, sale and transfer, encumbrance and pledge of fixed
              assets, including real property, buildings and rights of a real
              property nature, if the transaction value in each individual case
              is in EXCESS of DM 500,000 (in words: Deutsche Mark five hundred
              thousand);

         (f)  entering into or amending any contract with a value of more than
              DM 500,000 (in words: Deutsche Mark five hundred thousand);

         (g)  taking up and granting of loans and credits, assumption of
              guarantees, strict guarantees and other liabilities of the
              similar nature if the transaction value in each case is in excess
              of DM 500,000 (in words: Deutsche Mark five hundred thousand);

         (h)  any of the transactions and matters listed and referred to under
              sub-para. (a) through (g) above carried out by VuCo in its
              capacity as general partner of VuCo GmbH & Co. for and on behalf
              of VuCo GmbH & Co.

3.2 The approval of the Advisory Board to be obtained pursuant to para. 3.1
    above may also be made in form of a general authorization for particular
    types of the aforementioned transactions and matters.  Any such general
    authorization must precisely describe the transactions and matters in
    question as well as the purpose and the time frame in which they must be
    completed.


<PAGE>

                                          5



4.  ADVISORY BOARD

    4.1  The Advisory Board shall be composed of 4 (four) members. Each Party
         shall appoint two members (including one senior member).

    4.2  The Advisory Board shall advise the management and shall consider for
         approval the consents required according to Sect. 3.1. The Chief
         Executive Officer of VuCo GmbH shall be nominated by the Advisory
         Board to the Shareholders for appointment.  The Advisory Board shall
         negotiate and determine the employment contract with the Chief
         Executive Officer.

    4.3  The Advisory Board shall resolve its decisions with a simple majority
         of its votes, In the event that a majority decision cannot be reached,
         the following special procedures shall be used to break the deadlock:

         (a)  the Senior Advisory Board Member appointed by Behringwerke,
              following reasonable consultation with the Senior Member
              appointed by the other party. shall have the decisive vote in
              matters relating to the following agreements:

              [CONFIDENTIAL TREATMENT REQUESTED]


<PAGE>

                                          6



         (b)  the Senior Advisory Board Member appointed by Buyer, following
              reasonable consultation with the Senior Member appointed by the
              other party, shall have the decisive vote in all other matters.

    4.   The Advisory Board shall meet at least every 14 months or whenever
         requested by the Chief Executive Officer or by any of the senior
         members of the Advisory Board.  The meetings can be held by telephone
         or video conference.  Meetings shall convene with a notice period of 7
         (seven) days if not otherwise unanimously agreed.  Action can be taken
         by unanimous written consent.  The Advisory Board may adopt its own
         internal rules of procedure to be adapted from time to time.

5.  EXERCISE OF VOTING RIGHTS

    5.1  Shareholders' resolutions or partners' resolutions in shareholders'
         meetings, as the case may be, regarding the following matters shall
         require a unanimous vote of the shareholders or the partners:

         (a)  matters concerning capital increases and capital decreases.

         (b)  appointment of the Chief Executive Officer.

         (c)  appointment of the Companies' auditors, determination
              (FESTSTELLUNG) of the annual financial statements and profit
              distributions including distributions of reserves (RUCKLAGEN):

         (d)  exoneration (ENTLASTUNG) of the managing directors.

         (e)  amendments of the Articles or the Partnership Agreement to the
              extent that such amendments relate to, or have an impact on, any
              of the matters stipulated, mentioned or referred to in this
              Shareholders' Agreement:

         (f)  transformation (UMWANDLUNG) of the Companies as defined in Sec. 1
              Umwandlungsgesetz or dissolution of the Companies:


<PAGE>

                                          7



         (g)  entering into, amendment and termination of enterprise contracts
              (UNTERNEHMENSVERTRAGE);

         (h)  transfer of any decision powers of shareholders' meeting of VuCo
              GmbH or the partners"meeting of VuCo GmbH & Co. to any
              committees;

         (i)  the sale or acquisition of assets having a value in excess of DM
              50 million;

         (j)  debt financing in excess of DM 50 million, other than financing
              of accounts receivable;

         (k)  matters relating to the Overview Agreement after the consent and
              approval contemplated by section 5.1.4 of the Purchase Agreement
              has been obtained;

         (1)  matters relating to the Sales Promotion and Consignment Agreement
              between Behringwerke and Centeon Pharma dated September 28, 1995
              and effective as of July 1, 1995.

    5.2  If Behringwerke and Buyer are unable in two consecutive shareholders'
         meetings or partners' meetings, as the case may be, to reach an
         unanimous decision on matters requiring their unanimous vote and if
         they have not been able to resolve the matter within 30 days after the
         date of the second shareholders' meeting or partners' meeting, then
         Behringwerke and the Buyer can submit this matter to the respective
         member of the management board (VORSTAND) of Hoechst AG in charge of
         the business activities conducted by Behringwerke and of Guarantor for
         resolution.  They shall meet as necessary in order to discuss and
         resolve the matter by mutual agreement considering, if feasible, the
         use of expert advisors.

    5.3  With regard to matters other than those listed and referred to in
         para. 4.3.a and 5.1 above, Behringwerke shall exercise its voting
         rights in shareholders' meeting of VuCo GmbH and partners' meetings of
         VuCo GmbH & Co. consistent with the manner in which the Buyer
         exercises its voting rights it being under-


<PAGE>

                                          8



         stood that with regard to the matters listed and referred to in para
         5.1 above, Behringwerke may exercise its voting rights at its free
         discretion.

6.  TRANSFER, ASSIGNMENT OR ENCUMBRANCE OF SHARES OR INTERESTS

    The Parties agree that any transfer, assignment or encumbrances of shares
    or interests in VuCo GmbH or VuCo GmbH & Co. or parts thereof requires the
    prior written consent of the other shareholder or partner not to be
    unreasonably withheld, PROVIDED THAT no consent shall be required if (i)
    the shares or interests are transferred, assigned or encumbered to, or for
    the benefit of a wholly-owned subsidiary of the respective
    shareholder/partner and (ii) such shareholder/partner has proven to the
    other shareholder/partner by submission of a written agreement that such
    subsidiary has agreed to be bound by the terms of this Agreement pursuant
    to Sect. 11.

7.  AMENDMENTS OF ARTICLES OF ASSOCIATION AND PARTNERSHIP AGREEMENT

    Insofar as amendments of the Articles and the Partnership Agreement or any
    other resolutions are necessary or expedient for the execution and
    implementation of the provisions of this Shareholders' Agreement,
    Behringwerke and the Buyer shall procure that the appropriate resolutions
    are passed and all other necessary actions are taken promptly after the
    Closing Date.


8.  Financials; Information

    8.1  The financial statements of VuCo GmbH and VuCo GmbH & Co. shall be
         audited by an auditor (WIRTSCHAFTSPRUFER) nominated by the
         shareholders' meeting.

    8.2. Each Shareholder shall have the right to inspect (either itself or by
         advisors subject to a professional obligation of secrecy) during
         normal business hours (and at other times by agreement) all books,
         records and other information maintained for or by the Companies and
         (to the extent legally permissible) those maintained for or by its
         associated undertakings.  The right to inspect shall include the right
         to take copies.  Each Shareholder shall also have the right of


<PAGE>

                                          9



         access to the Companies' premises (either itself or by advisors
         subject to a professional obligation of secrecy) during normal
         business hours (and otherwise by agreement) for the above purpose and
         to inspect and review the premises.

9.  Duration

    This Agreement shall take effect as of the Closing Date and shall expire

    (a)  as of the date of notarization of the acceptance of the Behring Put
         Option or the Chiron Call Option, as the case may be, pursuant to Art.
         3 of the Purchase Agreement, or

    (b)  as of the date at which the right of Behringwerke to exercise the
         Behringwerke Put Option and the right of the Buyer to exercise the
         Chiron Call Option pursuant to Art. 3 of the Purchase Agreement has
         expired, or

    (c)  at such other date on which the Parties have mutually agreed.

10. NO PARTNERSHIP

    None of the provisions of this Agreement shall be deemed to constitute a
    partnership between the Shareholders and neither of them shall have any
    authority to bind the other in any way.

11. SUCCESSORS AND ASSIGNMENTS

    This Agreement shall enure for the benefit of and be binding on the
    respective successors in title and permitted assignees of each Shareholder
    which shall procure prior to the transfer of any of its Shares that each
    such transferee shall enter into a written agreement with the other
    Shareholders by which the transferee agrees to be bound by terms identical,
    mutatis mutandis, to the terms of this Agreement (including the terms of
    this clause as regards any subsequent transfer of the Shares).


<PAGE>


                                                            Annex 4.6 to the
                                                            Purchase Agreement





                          [CONFIDENTIAL TREATMENT REQUESTED]

                                     (1 Page)






<PAGE>

                                                              Annex 4.7 to the
                                      to the Purchase and Assignment Agreement

                       TERMS AND CONDITIONS FOR COMMISSION




1.  Under Art. 4.7 of the Purchase and Assignment Agreement, Buyer agrees to 
    pay Behringwerke, in addition to the Fixed Cash Purchase Price and the 
    Option Purchase Price, a yearly Commission on the sales of Guarantor's 
    and its affiliates' vaccine products listed on ANNEX 1 hereto for use in 
    Germany during the years 1997 through 2001, calculated as [CONFIDENTIAL
    TREATMENT REQUESTED] of the excess of net sales over the following 
    forecast:


    -     1997:    DM [CONFIDENTIAL TREATMENT REQUESTED]

    -     1998:    DM [CONFIDENTIAL TREATMENT REQUESTED]

    -     1999:    DM [CONFIDENTIAL TREATMENT REQUESTED]

    -     2000:    DM [CONFIDENTIAL TREATMENT REQUESTED]

    -     2001:    DM [CONFIDENTIAL TREATMENT REQUESTED]


    Such figures shall be adjusted for actual inflation on the basis of a 
    consumer price index (four-person-households average income) from 
    Closing Date to December 31 of each of the above-mentioned years.


2.  Buyer shall submit to Behringwerke by March 31 of the years 1997 through 
    2002 an auditable calculation and documentation of the total sales of 
    Buyer's vaccine products in Germany.


3.  The Commission shall be due and payable on March 31 of each respective 
    year.  Payment shall be made in Deutsche Mark by wire transfer free of 
    cost to the account of Behringwerke listed in clause 4.4 of the Purchase
    and Assignment Agreement in time to be received on the respective due 
    date.  Late payments shall bear interest at discount rate plus three 
    basis points.


4.  Behringwerke's experts (as designated by Behringwerke and reasonably 
    acceptable to Buyer) shall be entitled to audit, together with the 
    respective department of

<PAGE>

                                       2




    Buyer, any such calculations presented by Buyer, shall have reasonable 
    access to the business sites of Behring Vakzine GmbH & Co. or any 
    successor and to all books, records and other documents relating to such 
    calculation, and shall obtain from Buyer all information reasonably 
    requested.  The persons performing such audit on Behringwerke's behalf 
    shall treat confidential any information that they had access to, shall 
    use such information solely for the purpose of confirming the amounts due 
    hereunder, and shall report to Behringwerke's management exclusively.


5.  To the extent an audit pursuant to clause 3 above reveals any differences 
    from the calculation presented by Buyer, the balance shall be settled in 
    accordance with clause 3 within four weeks after the parties agreed on 
    such difference.


6.  As used herein, "net sales" means the amount invoiced for sales to 
    unaffiliated third parties of Guarantor, less (i) discounts, rebates, 
    chargebacks and allowances, (ii) returns, credits, recalls and 
    withdrawals, (iii) freight, insurance and packaging, (iv) V.A.T. and 
    other excise taxes, duties and other governmental charges, all to the 
    extent any of these are applicable to such sales.


<PAGE>





                                                                      Annex 1 of
                                             Annex 4.7 of the Purchase Agreement





                          [CONFIDENTIAL TREATMENT REQUESTED]

                                    (1 page)


<PAGE>



                                                                   Annex 7.1.16
                                                       to the Purchase Agreement






                          [CONFIDENTIAL TREATMENT REQUESTED]

                                    (1 page)


<PAGE>


                                                                  Annex 7.1.18
                                                         to Purchase Agreement





                          [CONFIDENTIAL TREATMENT REQUESTED]

                                    (1 page)


<PAGE>


                                                                 Annex 7.1.19
                                                    to the Purchase Agreement






                          [CONFIDENTIAL TREATMENT REQUESTED]

                                    (2 pages)

<PAGE>

                                                                  ANNEX  8



                                                      to Purchase Agreement





Use of name:

-  Chiron Behring Biocine GmbH

-  Chiron Behring Biocine GmbH & Co. KG


Use of logo:


BEHRING


<PAGE>

                                                                     ANNEX  11



                                                         to Purchase Agreement





                              HOECHST AKTIENGESELLSCHAFT
                                           



Chiron Corporation 
4560 Horton Street
Emeryville, CA   94608-2916

USA                                                           February 6, 1996



Ladies and Gentlemen:

Referring to the Purchase and Assignment Agreement to be entered between Chiron
GmbH and Behringwerke Aktiengesellschaft relating to the human vaccine business
of Behringwerke Aktiengesellschaft we confirm the following:

1.  For a period of five (5) years from the Closing Date of the aforementioned
    Purchase and Assignment Agreement (the "Protected Period") Hoechst and
    affiliated companies within the meaning of Section 18 of the German Stock
    Corporation Law (Aktiengesetz) will refrain from developing, marketing,
    producing, selling or otherwise distributing human prophylactic vaccines
    against infectious diseases.

2.  This obligation of non-competition shall be applicable worldwide, but for
    the following:

    Hoechst Ag owns a [Confidential Treatment Requested].  In addition, certain
    Hoechst AG affiliates manufacturer and sell human vaccine products
    [Confidential Treatment Requested].  Hoechst commits that none of these
    aforementioned affiliates will [Confidential Treatment Requested].

3.  Hoechst AG shall continue with VuCo GmbH & Co. the existing arrangements
    between Behringwerke and Hoechst AG with respect to the distribution of
    human vaccine products outside Germany at arm's length terms to be agreed
    upon, for not less than [Confidential Treatment Requested].

<PAGE>

                                                                      ANNEX 11

4.  In the event that, within 5 years from the Closing Date, VuCo proposes to
    have developed a human vaccine that is covered by an existing Hoechst AG
    patent, VuCo shall have the right to obtain a license under such patent for
    such product on commercially reasonable terms.

5.  Hoechst hereby consents to clause 3.5 of the Contribution Agreement as it
    relates to Hoechst patents.


Yours Sincerely,


HOECHST AKTIENGESELLSCHAFT


<PAGE>


                         [CONFIDENTIAL TREATMENT REQUESTED]

[Certain confidential information has been omitted from the Agreement and filed
separately with the Securities and Exchange Commission pursuant to a request by
Registrant for confidential treatment pursuant to Rule 24b-2.  The omitted
confidential information has been identified by the following statement:
"CONFIDENTIAL TREATMENT REQUESTED".]

                        CLOSING AGREEMENT

by and among

Behringwerke Aktiengesellschaft
D-30501 Marburg
represented by its members of the Management Board,
Prof Dr. Dr. Uwe Bicker and Dr. Bernd Neuefeind

(hereinafter "Behringwerke")

                                                          - on the one side -

and

Chiron Corporation

4560 Horton Street, Emeryville, CA 94608-2916, U.S.A.
represented by its Chairman of the Board,
Dr. William J. Rutter

(hereinafter "Chiron")

and

31. CORSA Verwaltungsgesellschaft mbH

represented by power of attorney by
Dr. Dino Dina,

(hereinafter "31.  CORSA")

                                                          - on the other side -


(Behringwerke, Chiron and 31. CORSA are hereinafter collectively referred to as
the "Parties" or, individually, as the "Party", as the context requires.)


<PAGE>

    PREAMBLE

A.  On February 17, 1996, the Parties entered into a Purchase and
    Assignment Agreement (Notarized Deed A. Prot. 1996/20 of the notary public
    Dr. Werner Wenger in Basle - hereinafter the "Purchase Agreement") with
    respect to the transfer 49% of the interests in a newly organized limited
    partnership which will continue to operate the human vaccine business of
    Behringwerke under the name Chiron Behring GmbH & Co (presently registered
    under the name Behring Vakzine GmbH & Co) and the transfer of a share in
    the nominal value of DM 24,500 in Chiron Behring Biocine GmbH
    Verwaltungsgesellschaft (which will be renamed into and referred to
    herein- after as "Chiron Behring GmbH") being the general partner of Chiron
    Behring GmbH & Co (hereinafter collectively the "Interests").

B.  Under the Purchase Agreement, the effectiveness of the transfer of
    the Interests requires the fulfillment of certain conditions.  The Parties
    now wish to clarify the status of and to modify such conditions.

C.  The Parties also wish to amicably settle certain issues which have come
    to their attention since the execution of the Purchase Agreement.

    NOW, THEREFORE, the Parties agree as follows:


    1.   FULFILLMENT OF CONDITION

         1.1   Behringwerke hereby declares that

              (i)  Chiron Behring GmbH & Co is holding all official
                   approvals for the operation of the Business (as defined in
                   the Purchase Agreement) as currently conducted pursuant to
                   the ARZNEIMITTELGESTZ, GENTECHNIKGESETZ, TIERSCHUTZGESETZ
                   and BUNDESSEUCHENGESETZ;


              (ii) the Operating Lease Agreement between Behringwerke
                   and Chiron Behring GmbH & Co will terminate with effect as
                   of the Closing Date (as defined hereinafter);

              (iii)the Contribution Date pursuant to the Contribution Agreement
                   (all as defined in the Purchase Agreement) has occurred on
                   April 1,  1996;

              (iv) Behring Vakzine GmbH (formerly the Institut fur
                   Produkttest und Verbrauchsforschung GmbH) is no longer a
                   general partner of Chiron Behring GmbH & Co and Chiron
                   Behring GmbH is now the sole general partner;


<PAGE>

              (vi) the management of Chiron Behring GmbH has agreed to
                   the split of one of the shares of Behringwerke in Chiron
                   Behring GmbH with a nominal value of DM 25,000 into two
                   shares with nominal values of DM 24,500 and DM 500,
                   respectively, and to the transfer of the DM 24,500 share to
                   31. CORSA.

         1.2  Chiron hereby declares that the necessary merger control
              approval for the implementation of the Purchase Agreement has
              been granted.

         1.3  Subject to the provisions of clause 6, the Parties
              mutually waive the condition stated in clause 5.1.4 of the
              Purchase Agreement, i.e., [CONFIDENTIAL TREATMENT REQUESTED]

              During the interim period until the assignment of [CONFIDENTIAL
              TREATMENT REQUESTED] is effected with or without amendments, 
              Behringwerke shall internally place Chiron Behring GmbH & Co as 
              it would be if such assignment had been effected as of the Closing
              Date (as defined hereinafter).


    2.   PAYMENT OF THE PURCHASE PRICE

         2.1  The Parties are in agreement that 31. CORSA shall pay the
              purchase price for the Interests in the amount as agreed in
              clause 4 of the Purchase Agreement (i.e., DM 171,813,430.40, of
              which DM 313,430.40 represents 49% of the rent under the
              Operating Lease Agreement) on July 1, 1996 to be received by,
              Behringwerke by 11:00 h on such date on the following bank
              account:

                        COMMERZBANK AG, FRANKFURT A.M.-HOCHST
                                ACCOUNT NO.: 251 57 57
                           BANK SORT CODE (BLZ): 500 400 00

              Behringwerke hereby warrants that Chiron Behring GmbH & Co has
              received prior to July 1, 1996 a rent under the Operating Lease
              Agreement (as defined in the Purchase Agreement) for the months
              of April through June in an amount of DM 639,653.88 (plus V.A.T.
              if applicable).  Behringwerke shall promptly deliver to 31 CORSA,
              with a copy to Chiron, written evidence (bank statement) of such
              receipt.

         2.2  Upon receipt of the purchase price, Behringwerke shall
              immediately deliver to 31 CORSA a receipt of the purchase price
              received.  Such receipt shall be forwarded first by telecopy and
              then by overnight courier to the attention of Ms. Jessica Hoover
              at Chiron, Emeryville.


<PAGE>

3.  CLOSING DATE

    Under the condition that Behringwerke has received the purchase price for
    the Interests as agreed in clause 2 above, the transfer of the Interests
    shall be effective as of July 1, 1996, 0:01 h (the "Closing Date").


4.  GUARANTEE

    In accordance with clause 14.3 of the Purchase Agreement Chiron agrees to
    the following:

    In the event that Chiron does not exercise the Chiron Call Option by March
    31, 1998, and if at that time or any time thereafter the long term credit
    rating of Chiron's senior debt securities falls below grade "A" of Standard
    & Poor's rating or Moody's comparable rating, Chiron will provide a letter
    of credit from a commercial bank, acceptable to Behringwerke, or other
    credit support fully satisfactory to Behringwerke, in an amount sufficient
    to satisfy 31. CORSA's obligation to pay the Option Purchase Price
    (assuming Behringwerke exercise the Behring Put Option in March 2001).

    The foregoing is deemed to satisfy in full Chiron's obligations under
    clause 14.3 of the Purchase Agreement.


                           [CONFIDENTIAL TREATMENT REQUESTED]


<PAGE>


                           [CONFIDENTIAL TREATMENT REQUESTED]


6.  PARTNERSHIP AGREEMENT

    The Parties are in agreement that promptly hereinafter and with effect as
    of the Closing Date, Behringwerke, 31. CORSA and Chiron Behring GmbH shall
    enter into the Partnership Agreement as agreed in the Purchase Agreement.
    The Parties shall promptly procure the necessary filings at the competent
    commercial register with respect to the registration of 31. CORSA as a new
    limited partner (Kommanditist) in Chiron Behring GmbH & Co.


7.  CASH MANAGEMENT

    Behringwerke hereby informs Chiron that Hoechst AG has agreed in the time
    being and until further notice (which will not be given prior to September
    30, 1996) to finance any negative cash flow of Chiron Behring GmbH & Co up
    to an aggregate outstanding amount of DM 20,000,000. at an interest rate of
    DM LIBOR plus 0. 125 % p.a. for credits with a mutually fixed term not
    exceeding six months, and an interest rate equivalent to the then
    applicable call money rate plus 0.125% p.a. for call money credits.
    Details will be agreed upon for each individual credit in compliance with
    the then applicable rules of "Konzeminterner Finanzausgleich" (Group
    internal Borrowing and Lending) and/or "Tagesgeld-Aufnahme und Anlage"
    (Group internal Call Money Arrangements) of Hoechst AG.  Chiron hereby
    unconditionally guarantees repayment of any such credit by Chiron Behring
    GmbH & Co when due.


8.  MISCELLANEOUS


    8.1  Unless otherwise expressly stated herein, all terms of the
         Purchase Agreement shall remain in force.

                           [CONFIDENTIAL TREATMENT REQUESTED]


<PAGE>


                           [CONFIDENTIAL TREATMENT REQUESTED]


<PAGE>

IN WITNESS HEREOF, the Parties have executed this Closing Agreement in triple
originals by their respective, duly authorized Board Members.



BEHRINGWERKE AKTIENGESELLSCHAFT

Date: June 29, 1996
By:



    /s/ Dr. Uwe Bicker
-------------------------------------------------
    (Prof. Dr. Dr. Uwe Bicker)



    /s/ Bernd Neuefiend
-------------------------------------------------
    (Dr. Bernd Neuefeind)


CHIRON CORPORATION

Date: June 29, 1996
By:



    /s/ Dr. William J. Rutter
-------------------------------------------------
    (Dr. William J. Rutter)


31. CORSA VERWALTUNGSGESELLSCHAFT MBH

Date: June 29, 1996
By:

    /s/ Dr. Dino Dina
-------------------------------------------------
    (Dr. Dino Dina)


<PAGE>

June 29, 1996



                          [CONFIDENTIAL TREATMENT REQUESTED]

[Certain confidential information has been omitted from the Agreement and filed
separately with the Securities and Exchange Commission pursuant to a request by
Registrant for confidential treatment pursuant to Rule 24b-2.  The omitted
confidential information has been identified by the following statement:
"CONFIDENTIAL TREATMENT REQUESTED".]



Behringwerke Aktiengesellschaft
D-30501 Marburg
Germany


Re: Closing Agreement dated June 29, 1996 between Chiron Corporation, 31 CORSA
    and Behringwerke AG


Gentlemen:

As set forth in clause 1.3 of the Closing Agreement, Chiron Corporation and 31
CORSA have agreed to waive the condition stated in clause 5.1.4 of the Purchase
Agreement.  Such waiver is conditioned upon the following agreement:


(a) Subject to paragraph (b) below, in the event that [CONFIDENTIAL TREATMENT
    REQUESTED] Behringwerke shall fully indemnify Chiron Behring GmbH & Co for 
    any damage suffered.  This damage shall be calculated on the basis of the 
    time period of [CONFIDENTIAL TREATMENT REQUESTED]

(b) The obligation of Behringwerke to indemnify Chiron Behring GmbH & Co under
    paragraph (a) is limited to an amount equal to [CONFIDENTIAL TREATMENT
    REQUESTED]

(c) In the event that the [CONFIDENTIAL TREATMENT REQUESTED] are not assigned to
    Chiron Behring GmbH & Co by November 30, 1996 each party shall be entitled
    to rescind the Closing, in which case Behringwerke shall pay back to 31.
    CORSA any purchase price paid plus an interest of 5.125% p.a. and 31. CORSA
    shall retransfer to Behringwerke the Interests.  Any additional damages by
    either party is excluded, other than for damages incurred as a result of a
    breach by either party of their obligation under clause d.



<PAGE>

June 29, 1996

Behringwerke Aktiengesellschaft




(d) Subject to the foregoing, the Parties will use their best efforts to ensure
    that the assignment [CONFIDENTIAL TREATMENT REQUESTED] occurs as soon as 
    possible and  [CONFIDENTIAL TREATMENT REQUESTED].


If the foregoing accurately reflects your understanding of our agreement, please
sign a copy of this letter for our records.

Very truly yours,


CHIRON CORPORATION

By:      /s/ William J. Rutter
       --------------------------
         William J. Rutter
         Chairman


31. CORSA Verwaltungsgesellschaft mbH

By:      /s/ Dino Dina
       --------------------------
       Dino Dina, pursuant to a power of attorney


Agreed and Accepted:


BEHRINGWERKE AKTIENGESELLSCHAFT

By:      /s/ Dr. Dr. Uwe Bicker
       --------------------------
       Prof. Dr. Dr. Uwe Bicker

By:      /s/ Dr. Bernd Neuefeind
       --------------------------
       Dr. Bernd Neuefeind