EXHIBIT 10.58


                      DESCRIPTION OF CHIRON'S 1996
              EXECUTIVE OFFICER VARIABLE COMPENSATION PROGRAM

     The compensation of Chiron's executive officers (including annual 
variable cash compensation) is determined by the Compensation Committee of 
the Board of Directors.  For 1996, the Compensation Committee continued the 
Company's approach that base salaries for executive officers generally should 
be targeted to the median (50th percentile) of salaries for benchmark 
positions in comparator companies.  Variable cash compensation for executive 
officers overall was targeted to yield total cash compensation at the 50th 
percentile, but with the opportunity to receive total cash up to the 75th 
percentile, as shown by comparative data, based upon individual, business 
unit, and overall Company performance.

     In evaluating the Company's overall performance in 1996, the Committee 
reviewed the quantitative Measurement Standard adopted by the Board pursuant 
to the Governance Agreement with Novartis (successor to Ciba-Geigy, Ltd.).  
The Measurement Standard included: (i) relative total stockholder return 
measured against two indices of comparator companies, (ii) revenue and 
earning performance, and, (iii) measures of innovation based principally 
upon accomplishment of specific milestones.  While the Committee found the 
Measurement Standard to have been satisfied for 1996, it noted that the 
Company's overall performance against these quantitative measures was 
disappointing, principally because of low relative stock price appreciation. 
The 



Committee also evaluated the Company's performance from a qualitative 
perspective and concluded that continued strategic progress by the Company, 
particularly in integrating and positioning each of its business units for 
sustainable and profitable growth and to play an important role in the 
markets it serves, balanced the quantitative measures discussed above, with 
the result that the component of executive officer compensation that depends 
upon overall Company performance was slightly above the target level for 1996.

     The Committee also reviewed management's quantitative assessment of the 
performance of each business unit in 1996 as measured by the specific 
"performance metrics" established for each unit.  These metrics included 
financial targets and specific innovation milestones linking each unit's 
contribution to the Company's overall performance on the Measurement Standard 
described above.

     Chiron's 1995 Executive Officer Variable Cash Compensation Plan, a 
performance-based plan qualifying for certain income tax benefits under 
Section 162(m) of the Internal Revenue Code, was not used in 1996.

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