The possible role of cerebral birth injury in the aetiology of epilepsy was evaluated by comparing the birth histories of 101 epileptic patients with focal seizures and 208 with non-focal seizures. The former were smaller at birth and their mothers were older and had higher blood pressures than the mothers of the latter. Although the two groups did not differ significantly with regard to the frequency of breech birth, assisted vaginal breech deliveries were significantly more numerous in the focal group. The injured half of the brain was as often pressed against the sacrum as against the symphysis during birth.