A technique is described for comparing graphically the electrostatic properties of molecules. Results from quantum mechanical calculations are mapped onto the van der Waals surface. The surface is defined by CSG (constructive solid geometry), a technique used in CAD (computer-aided design). Colour is used to represent the electrostatic properties and the results are displayed on a high resolution raster device as a 'realistic' model. This technique is expected to be of value in discriminating qualitatively between compounds of different biological activities. © 1984.