Investigation of the binocular functions in 25 patients with bilateral aphakia having undergone the two cataract operations at intervals ranging from 1 to 11 years. Only in 4 patients was the unilateral aphakia corrected temporarily by contact lenses. By the alternating cover test it was found that, after the second operation, 3 patients showed an esotropia and 14 an exotropia or exophoria for distant sight and 23 an exotropia or exophoria for near sight. Over one-third of the patients not having worn any contact lenses had no simultaneous vision at the Bagolini test for distant sight and more than half of them had no simultaneous vision for near sight. There was no stereoscopic vision for distant sight in nearly 50 % of the patients and no stereoscopic vision for near sight in more than half of those who had not worn any contact lenses. The early fitting of contact lenses or the immediate lens implantation in elderly patients together with the prescription of spectacles for near work in the case of unilateral aphakia prevent the weakening or the loss of binocular functions.