CABOT CORP — Director's Dealing 2005

Dec 20, 2005

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: CABOT CORP (CBT)
CIK: 0000016040
Period of Report: 2005-12-16

Reporting Person: GORMISKY PAUL J (Vice President)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2005-12-16	Common Stock	S	400	$34.72	Disposed	87821	Direct
2005-12-16	Common Stock	S	100	$34.73	Disposed	87721	Direct
2005-12-16	Common Stock	S	500	$34.76	Disposed	87221	Direct
2005-12-16	Common Stock	S	600	$34.82	Disposed	86621	Direct
2005-12-16	Common Stock	S	400	$34.85	Disposed	86221	Direct
2005-12-16	Common Stock	S	100	$34.86	Disposed	86121	Direct
2005-12-16	Common Stock	S	700	$34.87	Disposed	85421	Direct
2005-12-16	Common Stock	S	200	$34.88	Disposed	85221	Direct
2005-12-16	Common Stock	S	1000	$34.89	Disposed	84221	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	5887.96	Indirect

Holdings (Derivative)

Security	Exercise Price	Expiration	Underlying	Shares	Ownership
Series B ESOP Convertible Preferred Stock	$		Common (2083.05)	14.23	Indirect

Footnotes

F1: Each share is convertible into 146.3782 shares of the Corporation's common stock.

F2: 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.