We have investigated aspects of visual acuity with monovision correction. Binocular distance visual acuity with monovision was approximately equal to monocular visual acuity for addition powers (monocular defocus) of +1.00 to +2.50 D, using both high and low contrast logMAR visual acuity charts. Neither the eye chosen to be defocused (dominant or nondominant) or pupil size (3.5, 5 and 7 mm) affected the binocular visual acuity loss with monovision for high contrast charts. We also investigated the effect of induced residual astigmatism (+0.50, +1.00, and -1.00 D) on binocular distance visual acuity in monovision correction. Residual astigmatism caused a significantly greater reduction of binocular visual acuity in the monovision condition than it did in normal binocular conditions. This effect appears to be related to a process of meridional interocular suppression. It may therefore be of clinical importance to correct low amounts of residual astigmatism in monovision corrections to provide optimum binocular visual acuity.