X0201 4 2004-02-02 0000706539 CHIRON CORP CHIR 0001229444 LANCE SEAN P 4560 HORTON STREET EMERYVILLE CA 94608 1 0 0 0 Common Stock 2004-02-02 4 M 0 9000 21.0625 A 31149 D Common Stock 2004-02-02 4 S 0 9000 51.53 D 22149 D Employee Stock Option (Right to Buy) 21.0625 2004-02-02 4 M 0 9000 D 1999-05-01 2008-03-18 Common Stock 9000 192000 D On September 26, 2003, reporting person adopted a pre-arranged trading plan in accordance with SEC Rule 10b5-1. The exercise and same-day sale transaction reported hereunder was made pursuant to reporting person's Rule 10b5-1 Sales Plan. Stock Option granted under the Chiron 1991 Stock Option Plan in transaction exempt under Rule 16b-3. 125, 000 shares vested on 05/01/99; 475,000 vested in 48 successive equal monthly installments beginning on the first annual anniversary of reporting person's employment; vesting of 75,000 shares was accelerated as of 05/17/01 because certain performance goals were attained; the remaining 75,000 vested as of 05/01/03. Sean P. Lance by Carolyn Mar-Andreotti as Atty-in-Fact 2004-02-02