CHIRON CORP
EXHIBIT 10.509
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<BR></FONT><FONT SIZE=2><B>EXHIBIT 10.509    <BR>  </B></FONT></P>

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<BR></FONT><FONT SIZE=2><B>DESCRIPTION OF CHIRON CORPORATION'S<BR>  2002 EXECUTIVE OFFICERS VARIABLE COMPENSATION PROGRAM    <BR>  </B></FONT></P>

<P><FONT SIZE=2>Decisions
on compensation (base salary and variable compensation) of Chiron Corporation's ('Chiron' or the 'Company') executive officers are made by the Compensation Committee of the Board of
Directors. </FONT></P>

<P><FONT SIZE=2>For
2002, the Compensation Committee continued the Company's approach that base salaries for executive officers should be measured by reference to the median (50th percentile) of salaries for
benchmark positions in comparator companies. Further, the Compensation Committee provided that a significant portion of total cash compensation (salary plus variable compensation) in the form of
annual variable cash compensation potential should be 'at risk,' dependent upon individual, business unit and overall Company performance. Variable cash compensation for executive officers overall was
targeted to yield total cash compensation at the 50% percentile, but with the opportunity to significantly exceed the 50% percentile of total cash compensation as shown by comparative data, in the
case of outstanding Company, business unit, and individual performance. </FONT></P>

<P><FONT SIZE=2>The
Compensation Committee based its decisions regarding variable compensation for executive officers upon its evaluation of performance against pre-established performance metrics developed at the
Company, business unit and functional or corporate unit level. </FONT></P>

<P><FONT SIZE=2>Variable
compensation for the Chairman and Chief Executive Officer is based on the performance of the Company as measured against the pre-established Company metrics composed of financial objectives
and technology and business innovation milestones. </FONT></P>


<P><FONT SIZE=2>Executive
officers responsible for business units or major functional or corporate units are eligible for variable compensation based on the pre-established Company metrics and on the achievement of
their respective business, functional, or corporate unit metrics. </FONT></P>

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<FONT SIZE=2><A HREF="#toc_ki1148_2">DESCRIPTION OF CHIRON CORPORATION'S 2002 EXECUTIVE OFFICERS VARIABLE COMPENSATION PROGRAM</A></FONT><BR>

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