Case-based reasoning is an area of artificial intelligence which deals with using past cases for solving new problems. Representation of design cases is an important issue in the development of case based design systems. The requirements of a representation scheme for design cases are discussed in this paper. A representation scheme has been proposed that enables not only browsing through past design cases, but also enables reasoning about the designs. The representation is based on an object oriented approach, upon which a reasoning mechanism called complementary view model is built. The components of the case base are described in order to bring out the use of the above mechanisms in their representation. © 1997 Civil-Comp Ltd and Elsevier Science Ltd. All rights reserved.