Subdural haemorrhages in the neonate are still rarely recognised clinically. This study was carried out using E.E.G. data obtained from 12 cases of subdural haemorrhages in full-term neonates, the diagnosis being confirmed at post-mortem. In 2 of the cases where the subdural haemorrhage was localised, the E.E.G. was moderately abnormal with depression of the background activity but without seizure activity and with preservation of sleep organisation. In the other 10 children, the subdural haemorrhage was associated with underlying cortical necrosis. All these recordings were markedly abnormal either inactive or paroxysmal or with low amplitude activity with interspersed sharp wave discharges. Two out of these cases had seizure activity on their trace. The sleep organisation, when appreciable had disappeared. The subdural haemorrhages were usually bilateral and when unilateral, localising signs (depression of activity on ipsilateral side of focal seizure activity) are of little help. The E.E.G. is in fact of little diagnostic value in neonatal subdural haemorrhage but enables the degree of underlying cerebral damage to be assessed.