A method is described which allows an investigation of the difficulties experienced by people when they attempt to understand engineering drawings. The method requires subjects to make comparisons between drawings of simple objects and solid models of the same objects. In one variant of the method, subjects have to recognize a model which matches the drawing given to them; in the other variant they have to assemble a model to match the drawing. Undimensioned ond dimensioned drawings wore prepared for each of four projection typos: (a) First Angle Orthographic, (b) Third Angle Orthographic, (c) Isometric and (d) True Perspective. The full series of eight drawings was presented to samples of draughtsmen and university Arts students of both sexes who were totally unfamiliar with engineering drawings. Results show the clear superiority of both representational projections for the tasks used as judged by criteria of speed and accuracy. The success of orthographic drawings was determined for the draughtsmen chi...