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                                                                   EXHIBIT 10.31

                         PACKARD AURORA SUPPLY AGREEMENT

        THIS AGREEMENT ("Agreement") is made and entered into as of the
Effective Date (wherein the "EFFECTIVE DATE" means the date that this Agreement
is executed by the last party to so execute) by and between Packard Instrument
Company, Inc., a State of Delaware corporation with its principal office at 800
Research Parkway, Meriden, Connecticut 06450 and Affiliates ("PIC"), and Aurora
Biosciences Corporation, a State of Delaware corporation with its principal
office at 11010 Torreyana Road, San Diego, California, 92121 and Affiliates
("ABSC"). This Agreement is entered into as agreed in the Collaboration and
License Agreement between ABC and PIC dated April 24, 1996 ("COLLABORATION
AGREEMENT"), Section 6.2.



                                    RECITALS

        ABSC and PIC (the "PARTIES") desire to enter into an agreement pursuant
to which *** therefor (the "PRODUCTS"), described in *** (the "***")*** (the
"PRODUCT DESIGN"), and (ii) *** (the "STANDARD INSTRUMENTS"), the Products and
Standard Instruments being referred to collectively in this Agreement as the
"COMPONENTS*** (the "SYSTEMS"). ***.



                                      TERMS

1.      SUPPLY OF PRODUCTS

*** the Products ordered in purchase orders submitted by *** pursuant to Article
3 and as set forth in this Agreement. *** will supply and manufacture such
Products in accordance with the Product Specifications and delivery times as set
forth herein. *** will allocate sufficient resources, capital equipment,
materials, tools and labor to accomplish its obligations herein.


2.      SPECIFICATIONS AND PRODUCT DESIGN

2.1 Specifications. The Product Specifications set forth in Exhibit A may be
modified from time to time by written agreement of the Parties. Products
supplied after such modification will conform to such modified Product
Specifications.




2.2     ***.


3.      PURCHASE ORDERS

3.1 Purchase Orders by ***. This Agreement shall not be construed as a purchase
order or as 


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authority to ship. Any such order or authority shall be evidenced by specific
and separate purchase orders issued by *** pursuant to this Section 3. All
purchase orders shall be governed exclusively by the terms and conditions of
this Agreement. In the event of a conflict between any terms or conditions in
this Agreement and those contained in the purchase orders, the terms and
conditions of this Agreement shall prevail.

3.2 Purchase and Supply Commitment for 1998*** a minimum ***, as described in
Exhibit A) and ***", as described in Exhibit A), subject to delivery by *** and
acceptance by *** under the terms of this Agreement. Purchase orders for such
Products will be submitted by *** in accordance with Section 3.3.

3.3 Quarterly Orders and Forecasts. During the Term of this Agreement (as set
forth in Section 11.1) ***, specifying the required delivery dates. At such time
***, provided that such forecast shall not constitute any commitment or
obligation whatsoever on the part ***.

3.4 Purchase Orders. In addition to the Quarterly Orders, ***. Such purchase ***
in advance of the required delivery date, unless a shorter lead-time is mutually
agreed to by the Parties.


4.      DELIVERY

4.1 Time of Delivery. Subject to Section 4.2 below, ***. Such delivery dates
shall not vary by more than ***, unless mutually agreed upon in writing by the
parties.

4.2 Acceptance. *** shall inspect, ***.

4.3 Defective Products. Within thirty (30) working days of receiving
notification of defective Products from *** shall (i) correct the defects, (ii)
replace the defective Products or (iii) grant *** a credit for such rejected
Products equal to the price paid therefor.

4.4 Late Delivery. If PIC is unable to deliver the Products on the date
specified in purchase orders where such purchase order is accepted and confirmed
in writing by PIC, PIC shall have thirty (30) days to cure late delivery. In the
event PIC fails to deliver Products within thirty (30) days of the date
specified on such purchase order, ABSC may, at ABSC sole discretion: (i)
reschedule shipment or (ii) be released from its obligation to purchase said
late Products.

4.5 Repeated Late Delivery. If, after delivery of *** and *** fails to deliver
on more than ***, a Product within the thirty day grace period, *** may, at its
sole discretion: (i) reschedule shipment, (ii) be released from its obligation
to purchase said late Products and/or (iii) ***, plus the length of time
required to manufacture such Products, and be provided promptly with all
drawings and documentation required thereto. The royalty to be paid by *** in
option (iii) above will be between *** of sales for such Products, the exact
percentage to be negotiated by the Parties. If *** cures the reason for the
delay to the reasonable satisfaction of *** and provides written notification of
the cure to ***, any remaining Product needed by *** at the time of such
notification will be purchased from *** subject to the terms of this Agreement,
the non-exclusive license provided for within this section 4.5 shall terminate
and all drawings and documentation 


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provided to *** under this section 4.5 shall be returned to ***.



5. LICENSE GRANT

PIC hereby grants to ABSC ***.

***.


6. FIELD REPAIR SERVICES

6.1 Services to ABSC by PIC. *** will provide at *** request field repair
services at ABSC's facilities. Such services will be provided by *** at no
charge to ABSC for one *** acceptance of a Component by ***. After the one
(1)-year period following acceptance of any Component, such services will be
provided by *** customary charges for servicing comparable equipment at
comparable customer locations.

6.2 Services to ABSC's Customers by PIC. *** will provide at *** request field
repair services for *** customers. PIC will provide such services for *** at
charges comparable to PIC's customary charges for servicing comparable equipment
at comparable locations for *** following acceptance of a Component by ***.
After the *** following acceptance of any Component, PIC will provide such
services for *** at *** customary charges on an annual service contract basis
for servicing comparable equipment at comparable customer locations.


7. PRICES AND PAYMENTS

7.1 Price Basis for Products.

        (a) The prices to *** plus the product of the cost of goods sold ***
times *** is less than or equal to *** or (ii) *** when *** is greater than ***.
The price to ABSC for all subsequent *** shall be (i) *** times *** when *** is
less than or equal to ***, or (ii) *** plus ***, when *** is greater than ***.
After the first six production quality units for a particular ***, in no case
will the price to *** be greater than the lowest price PIC charges to a third
party for such *** or a substantially similar ***. Supplied with each ***.

        (b) The prices to *** shall be (i) *** times *** when *** is less than
or equal to *** or (ii) *** plus *** when *** is greater than ***. The price to
ABSC for all subsequent *** shall be (i) *** times *** when *** is less than or
equal to ***, or (ii) *** plus *** when *** is greater than ***. After the first
six production quality units for a particular ***, in no case will the price to
*** be greater than the lowest price PIC charges to a third party for such ***
or a substantially similar ***.


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7.2 Inclusions to Prices. The prices for the Products are inclusive of all (i)
boxing, crating, containerizing, carting, drayage, storage, and packaging; (ii)
shipping to ABSC's facilities located in the United States including insurance
during shipment and (iii) spare parts as specified ***.

7.3 Time of Payment. Payment of *** of the total price will be made by ***
within *** after delivery of Product to *** facility. The remaining *** of the
total price will paid by *** within *** after acceptance by *** as set forth in
Section 4.2.

7.4 Payment Does Not Constitute Acceptance. Payment shall not constitute
acceptance of Products and shall be subject to adjustment for errors, shortage,
defects in Products or other failure of PIC to comply with the terms of this
Agreement. Acceptance shall be deemed to have taken place as set forth in
Section 4.2.

7.5 Audits. PIC shall maintain for *** from the date of manufacturing complete
and accurate records of the information necessary to determine the COGS and
calculate the pricing for each Product. ABSC shall have the right at ABSC's
expense to audit or have audited by an independent third party such records in
order to verify compliance of the pricing with terms of this Agreement. If such
an audit reveals an overcharge in excess of *** in a given ***, PIC shall adjust
the price to comply with this Agreement, credit *** for any overcharges paid by
*** during the applicable period and reimburse *** for the reasonable, direct
and necessary costs of the audit.


8.      REPRESENTATIONS AND WARRANTIES

8.1 Warranty on Products. PIC represents and warrants that all Products
including all parts, components and materials incorporated therein, will be ***.
All Products will be produced in accordance with and will conform to the Product
Specifications.

8.2 General Warranties of PIC. PIC further represents and warrants that:

        (a) PIC is free to enter into and perform this Agreement in all
respects;

        (b) in designing, manufacturing, assembling and otherwise producing
Products, PIC, to the best of PIC's knowledge, will not be in violation of or
infringing upon the rights of any third parties;

        (c) PIC 's entering into this Agreement does not violate any agreement,
right or obligation existing between PIC and any other person or entity.

8.3 General Warranties of ABSC. ABSC further represents and warrants that:

        (a) ABSC is free to enter into and perform this Agreement in all
respects; and

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        (b) ABSC 's entering into this Agreement does not violate any agreement,
right or obligation existing between ABSC and any other person or entity.


9.      INTELLECTUAL PROPERTY RIGHTS

Except as set forth in Article 5., intellectual property rights shall be
retained as set forth in Article VIII of the Collaboration Agreement.


10.     INDEMNITY

Indemnification shall be retained as set forth in Article IX of the
Collaboration Agreement.


11.     TERM AND TERMINATION

11.1 Term of Agreement. This Agreement shall have an ***.

11.2 Material Breach. Except as expressly set forth in this Agreement, either
party may terminate this Agreement if the other party breaches any of the terms
and provisions of this Agreement in a manner that is materially adverse to the
other party, and the breaching party fails to cure the breach within thirty (30)
business days after receiving notice from the other party specifying the
particulars of the breach; if such breach is not curable within thirty (30)
business days, the non-breaching party may terminate this Agreement as provided
above by giving written notice to the breaching party.

11.3 Survival of Rights. Termination of this Agreement shall be without
prejudice to any rights or claims which the nonbreaching party may otherwise
have against the other party. Sections 5, 6, 7.4, 8, 9, 10 and 11 shall survive
termination or expiration of the Agreement.

11.4 License to Manufacture. In the event PIC is unable to supply Products to
ABSC for a period of more than ***.


12.     CONFIDENTIAL INFORMATION

The terms for Confidentiality shall be retained as set forth in Article XI. of
the Collaboration Agreement.


13.     MISCELLANEOUS

13.1 Assignment and Binding Effect. Terms for assignment and binding effect of
this Agreement shall be as set forth in Section 12.2 of the Collaboration
Agreement.


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13.2 Independent Contractors. The Parties are acting as independent contractors
as set forth in Section 12.8 of the Collaboration Agreement.

13.3 Severability. The terms for severability are as set forth in Section 12.7
of the Collaboration Agreement.

13.4 Notices. The terms for notices are as set forth in Section 12.3 of the
Collaboration Agreement.

13.5 Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of California, without regard or giving
effect to its principles of conflict of laws.

13.6 Force Majeure. The terms for Force Majeure are as set forth in Section 10.5
of the Collaboration Agreement.

13.7 Arbitration. Any dispute shall be settled as set forth in Section 12.1 of
the Collaboration Agreement.



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13.8 Entire Agreement and Amendments. The terms for the entire agreement and
amendments of the Agreement are as set forth in Sections 12.6 and 12.5,
respectively, in the Collaboration Agreement.


IN WITNESS whereof the parties hereto have this day caused this Agreement to be
executed by their duly authorized officers.


AURORA BIOSCIENCES                          PACKARD INSTRUMENT
CORPORATION                                 COMPANY, INC.


By: /s/ CHARI STYLLI                        By: /s/ RICHARD T. MCKERNAN
   --------------------------------            ---------------------------------
Title: Vice President                       Title: President
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Date: February 5, 1998                      Date: February 5, 1998
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