The pathophysiology and outcome following severe head injury in 85 children are presented. The commonest initial CT diagnosis was of acute brain swelling. This swelling was associated with an increased white matter density on the CT scan which decreased to normal concomitant with recovery and increased ventricular size. CBF measurements in 6 of these patients revealed an increased blood flow despite a decreased CMRO2 and clinical coma. This CT pattern of diffuse swelling is believed to be due to acute cerebrovascular congestion and hyperemia and not to edema. Because of this, all children were treated with endotracheal intubation and controlled hyperventilation as part of the initial management. Mass lesions were uncommon, 20%. ICP was monitored in 40 children. The ICP rose above 20 Torr despite therapy in 80% of children with decerebrate or flaccid coma and in only 20% of children with spontaneous motor function. The ICP was at its highest between the second and fifth day. Aggressive therapy to control the ICP, with barbiturates if necessary, was successful in 80% of the patients. The overall results were useful recovery in 87.5% of the children, 3.5% were left vegetative or severely disabled and 9% died.