X0201 4 2004-02-13 0000706539 CHIRON CORP CHIR 0001233539 PATTERSON LEONE D 4560 HORTON STREET EMERYVILLE CA 94608 0 1 0 0 Vice President; Controller Common Stock 2004-02-13 4 A 0 1200 0 A 5564 D Employee Stock Option (Right to Buy) 51.98 2004-02-13 4 A 0 3900 A 2005-02-13 2014-02-13 Common Stock 3900 3900 D This total includes 2,300 share rights awarded pursuant to the Chiron 1991 Stock Option Plan in transaction exempt under Rule 16b-3, which share rights are subject to certain vesting. Employee Stock Option granted under the Chiron 1991 Stock Option Plan in transaction exempt under Rule 16b-3. Right to exercise vests as to 1/4 of the total shares on the first anniversary of the grant date and monthly thereafter as to 1/48 of the total shares, subject to acceleration of vesting upon certain qualifying terminations of employment. The Chiron 1991 Stock Option Plan has provisions permitting, in the discretion of the Administrator, the withholding of shares from the grant to satisfy income tax withholding. Leone D. Patterson by Carolyn Mar-Andreotti as Atty-in-Fact 2004-02-17