To provide sufficient numbers of patients varying in age of initial adequate surgical alignment for congenital esotropia, 162 patients managed by seven ophthalmologists in three countries were personally examined by the author and the results compiled for a clinical study. From this population group, 106 patients were chosen who had reliable answers, satisfactory alignment, and an ophthalmologist's confirmation examination of the congenital nature of the problem by at least 1 year of age. The results of sensory testing showed that those adequately aligned by the age of 6 months vs 12 months vs 24 months were not statistically different, but those patients aligned after 24 months of age demonstrated a significantly lower percentage with evidence for binocularity (P less than 0.001). Surgical alignment in the congenital esotropic patient should be accomplished by 2 years of age to attain the highest yield of binocular function.