EXHIBIT 10.314



                                 AMENDMENT NO. 2

                                       TO

               AGREEMENT BETWEEN GEN-PROBE INCORPORATED AND CHIRON
                                   CORPORATION

         This Amendment is made effective as of February 1, 2000, to the
Agreement between Gen-Probe Incorporated and Chiron Corporation dated as of June
11, 1998, as previously amended (the "Agreement").

         The parties hereby agree to amend the Agreement as follows:

         1. DEFINITIONS. Capitalized terms not defined in this Amendment
shall have the meanings set forth in the Agreement.

         2. APPLICABLE TO CHIRON AND GEN-PROBE ONLY. [PROVISION ASSIGNED].
Chiron retained all rights and obligations under the Agreement with respect
to the Blood Screening Field. This Amendment is effective as between Chiron
and Gen-Probe, [PROVISION ASSIGNED].

         3. CONFIDENTIALITY AND INVENTION OWNERSHIP.

            A. Section 1.23 of the Agreement is hereby amended by placing a
period (".") after the word "Agreement" at the end of clause (ii) in the first
paragraph, and deleting the following words:

            "and (iii) marked, identified as, or otherwise acknowledged to
            be confidential at the time of disclosure to the other party."

            B. Section 8.1 of the Agreement is hereby amended by deleting the
following sentence at the end of the Section:

            "Notwithstanding the foregoing and Section 1.23, unless otherwise
            mutually agreed in writing, neither party shall have any obligation
            to the other party pursuant to this Article 8 or pursuant to Article
            9 with respect to use of Confidential Information of the Disclosing
            Party unless, prior to disclosure, such Confidential Information is
            specifically identified in writing to the Receiving Party and the
            Receiving Party agrees in writing to accept such Confidential
            Information."



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            C. Section 9.1.4(b) of the Agreement is hereby amended to read in
full as follows:

            "(b) was made through or with, and would not have been made but for,
            the Inventing Party's use of Confidential Information of the other
            party (the "Disclosing Party"), if such information was confidential
            when the invention was made."

         By the signatures of their authorized officers below, Gen-Probe and
Chiron adopt this amendment as of February 1, 2000.


CHIRON CORPORATION                         GEN-PROBE INCORPORATED


By       /s/ RAJEN K. DALAL                By       /s/ HENRY L. NORDHOFF
         ------------------                         ----------------------
                                                    Henry L. Nordhoff
         Title: President,                          President and
         Blood Testing                              Chief Executive Officer
         Chiron





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