A method of characterizing the surface topography of wear particles by the application of computer image analysis to scanning electron microscope (SEM) stereoscopic pairs of images is proposed and described in this paper. The image analysis consists of noise reduction, edge detection, thresholding, stereoscopic matching, calculation of elevation points and interpolation. An improved automatic stereoscopic matching algorithm has been developed. The algorithm was initially applied to computer-generated images of a polished marble sphere and a polished marble cube and later to SEM images of wear particles found in artificial and synovial joints. The results demonstrate that SEM stereoscopy can successfully be used in the characterization and measurements of wear particle surface topography. (C) 1997 Elsevier Science S.A.