This paper presents the results of an experimental study in which solid spheres of various materials were plastically deformed between parallel platens. During the experiments the variation in the contact area and the area of the central plane of symmetry with plastic deformation were monitored. From these ares, two normalized parameters could be defined that were independent of size as well as material, thus indicating that the deformation is controlled, for the most part, by the geometry. It was also observed that radial expansion at the centre of the sphere started relatively late during deformation (7% macroscopic compressive strain). Microhardness mapping through the depth of some specimens confirmed this observation and yielded information about the distribution of the deformation fields within the sphere. It was seen that the measured microhardness values (and, thus, the plastic deformation fields) were radially symmetric in the planes perpendicular to the direction of the compressive load, reflecting the symmetry of the deformation geometry. © 1988 Taylor & Francis Group, LLC.