This work is based on the premise that life-cycle knowledge regarding the product and design process must be incorporated in the centre of CAD architecture. It focuses on the systematization and sharing of knowledge of many types in many places and is concerned with knowledge management over product life-cycle. The topics covered here include: ontology; knowledge-intensive CAD (KIC); knowledge-intensive design (KID); and knowledge representation for KIC. The papers represent some of the proceedings of the Third Workshop on Knowledge Intensive CAD, sponsored by Working Group 5.2 of the International Federation for Information Processing (IFIP) and held on December 1--4, 1998 in Tokyo, Japan.