Conceptual design is one of the few areas of engineering design where computers have yet to make an impact. With the development of Knowledge Based Systems it is now possible to rectify this situation. This publication deals with the use of Knowledge Based Systems (KBS) as tools for conceptual design. Included are neglected aspects such as evaluation and user needs. "Practical Knowledge Based Systems in Conceptual Design" is based on the authors' experience of developing KBS for use in civil engineering, an area of industrial application which is recognised as having great potential. The methodology has been tried and tested by designers. Examples of systems which have been developed to solve specific design problems are included.