The aim of this study was to investigate the incidence of squint after brain damage. We performed an observational study on 239 consecutive patients admitted to a specialist neurological rehabilitation unit: 129 with stroke, 84 with head injury and 26 with other conditions. Standard orthoptic measures, including visual acuity, cover test, eye movement recording and tests of binocular function were performed. Of all the patients, 89 (37%), were found to have squints, but only 32 of these (36%) experienced double vision. Brain stem lesions causing peripheral ocular motor impairment were found in a high proportion of patients after head injury (56%). Squints were found in 27 of 95 (28%) patients with cortical strokes, many with no other signs of brain stem involvement. Left was just as likely as right hemisphere damage to be associated with squint, but right-sided lesions seemed to protect against diplopia. We conclude that squint is common after brain damage, even if the brain stem is not obviously affected, but only a minority of these patients with acquired squint suffer diplopia.