The relationship between photophobia and binocular function in intermittent exotropia was examined in 42 subjects (21 patients and 21 controls). In all subjects fusional amplitude and strength of binocular sensory status were tested before and during exposure to bright light. An explanation of photophobia in intermittent exotropia was suggested as impairment in binocular cooperation, since the indicators of binocular function were significantly altered in the patients, particularly during light exposure.