Cabot Corporation Confirms Union Workers on Strike at its Cabot Supermetals Boyertown Facility

June 21, 2005

BOSTON and BOYERTOWN, Pa., June 21 /PRNewswire-FirstCall/ -- Cabot Corporation (NYSE: CBT) announced today that employees of Cabot Supermetals (CSM), who are members of the International Chemical Workers Union Council/United Food and Commercial Workers (ICWUC/UFCW, Local 619-C), elected to strike, effective June 20, 2005.

The parties have been in negotiations on a new collective bargaining agreement since March 31, 2005. The collective bargaining agreement between CSM and ICWUC/UFCW, Local 619-C expired on May 7, 2005. Union members have been working since that date without a contract.

During the work stoppage, CSM is committed to operating the plant safely and securely and is fully prepared to meet all customer needs. Contingency plans are in place and management is proceeding to implement those plans as needed.

Cabot Corporation is a global specialty chemicals and materials company headquartered in Boston, Massachusetts, USA. Cabot's major products are carbon black, fumed silica, inkjet colorants, capacitor materials, and cesium formate drilling fluids. The website address is: http://www.cabot-corp.com.

Contact:
Ethel Shepard
Corporate Affairs Manager
617-342-6254
ethel_shepard@cabot-corp.com

Susannah Robinson
Director, Investor Relations
617-342-6129
susannah_robinson@cabot-corp.com

SOURCE Cabot Corporation