IFIP Working Group 5.2 has organized a series of workshops extending the concept of intelligent CAD to the concept of "knowledge intensive engineering". The concept advocates that intensive life-cycle knowledge regarding products and design processes must be incorporated in the center of the CAD architecture. It focuses on the systematization and sharing of knowledge across the life-cycle stages and organizational boundaries. This text comprises the proceedings of the Fourth Workshop on Knowledge Intensive CAD, which was sponsored by the International Federation for Information Processing (IFIP) and held in Parma, Italy in May 2000. This workshop looked at the evolution of knowledge-intensive design for the product life-cycle moving towards knowledge intensive engineering. The 18 selected papers present an overview of the state-of-the-art in knowledge intensive engineering, discussing theoretical aspects and also practical systems and experiences gained in this area.