Changes in esotropia were studied in 50 patients who had undergone full-time occlusion therapy for strabismic amblyopia to investigate the possibility that occlusion may have an influence on the amount of a preexisting esodeviation. Angle measurements of 21 esotropic patients with an alternating fixation behavior who had not been treated by occlusion served as comparative data. Under occlusion, either an increase or a decrease of five or more prism diopters in the strabismic angles occurred in 58% (29/50) at near fixation and in 62% (28/45) at distance fixation. The amounts of change in the deviations were noted to be significantly higher in the children under 42 months of age. In the group of alternating esotropes, 57% (12/21) showed either an increase or decrease of five or more prism diopters at near fixation, and 65% (13/20) at distance fixation. Since there was no significant difference between the means of these changes in both groups of patients, it is unlikely that occlusion, per se, caused the variations in ocular alignment observed in the patients with strabismic amblyopia.