After a review of fundamental definitions in binocular vision-binocular convergence, retinal disparity and their perceptual correlates (fusion, diplopia, suppression and stereoscopic depth)-psychophysical data on Panum's area and their spatial and temporal characteristics are presented. Specific features of stereopsis as the visual perception of three-dimensional space based on binocular disparities are described: horizontal disparity processing for depth perception, global stereopsis according to Julesz, and the disparity gradient limit for binocular matching. A discussion of stereoscopic acuity and of the neurophysiological basis of stereopsis is also included.