Major changes in the demands of the automobile engineer have led to a reduction in variety, an increase in numbers and a change in materials used. More accurate production methods need more accurate castings and less is left to the judgement of the individual pattern-maker. Fundamental design problems are discussed, such as the uniqueness of component description and the difficulties with defining split lines and surfaces. Conventional methods of mould-making are outlined and details are given of A computer aided engineering system (duct) with stereoscopic viewing facilities. The system is shown diagrammatically and the various operational steps involved are explained. A review is given of the fundamental concepts involved in the use of duct to design components. An example is given of a mould made without the use of any conventional drawings. Weights of components can be quickly estimated, and components can easily be optimised for weight and casting stresses. (TRRL)