Visual acuity was measured in one eye during monocular vision, and while the fellow eye viewed stimuli not including the acuity target. The aim was to find how acuity in one eye is reduced by going from monocular to binocular viewing. In normal subjects, acuity was at its lowest during the suppressive phase of binocular rivalry, was reduced less when the fellow eye viewed a contoured nonrivalrous stimulus, and was not reduced at all when the stimulus to the fellow eye consisted of a uniformly lit field. In strabismic subjects, by contrast, acuity was markedly reduced in going from monocular to binocular viewing no matter what stimulus was viewed by the fellow eye. Pathological suppression is therefore largely independent of the inducing stimulus. It was also shown that acuity in the nonstrabismic eye of some of the strabismic subjects was improved by allowing the strabismic eye to view; these were the subjects with the greatest depths of amblyopia.