In a prospective study 76 children were divided into three groups on the basis of severity of head injury as defined by the Glasgow Coma Scale and duration of increased intracranial pressure. The children were administered a neuropsychological test battery and behavioural ratings were made by parents and teachers at three intervals: time of hospital discharge and 3 and 9 months post-initial testing. There were cognitive deficits related to severity of injury with the greatest difference in abilities observed between the severe and the other two groups. The greatest differences in skills were on the Performance IQ and timed tests of visual-motor speed and co-ordination. The greatest improvement in skills occurred in the first 3 months post-injury. Several children in coma for up to 4 weeks were able to obtain normal IQ scores. In the mild and moderate injury groups very few had behavioural change while in the severe group approximately 90% had one learning or adjustment difficulty and 40% had three or more problems.