X0201 42003-12-05 0000016040 CABOT CORP CBT 0001201082 BRADY WILLIAM J C/O CABOT CORPORATION TWO SEAPORT LANE, SUITE 1300 BOSTON MA 02210 0100Executive Vice PresidentCommon Stock2003-12-054S0418330.48D122640DCommon Stock5108IThrough the Trustee of the Corporation's Retirement Savings Plan.Series B ESOP Convertible Preferred StockCommon stock837757IThrough the Trustee of the Corporation's Retirement Savings Plan.Each share is convertible into 146.4 shares of the Corporation's common stock.Under the Retirement Savings Plan, the Corporation allocates Series B ESOP Convertible Preferred Stock to each participant's account on a quarterly basis. Subject to certain terms and conditions of the Retirement Savings Plan, participants may elect to receive distributions of their vested account balance in the form of shares of the Corporation's common stock or cash. Generally, a participant is 20% vested in his account after 2 years of service with the Corporation; 40% vested after 3 years of service; 60% vested after 4 years of service; and 100% vested after 5 years of service.Michaela Allbee, pursuant to a power of attorney from William Brady2003-12-09