The frequency of behavioural disturbances early after injury in relation to outcome was prospectively investigated in a series of 67 patients with mild-to-moderate head injury (as defined by GCS on admission). In more than half of the patients, behavioural disturbances were observed. Restlessness occurred in 40% of patients, whereas agitation was seen in 19% of patients. In all patients, restlessness and agitation disappeared before resolution of PTA. In multiple regression analysis, restlessness and PTA were found to be separate factors in predicting outcome. On imaging studies, twice as many lesions were seen in patients with restlessness and agitation (81% compared to 39%), mainly localized in the frontotemporal region. In two thirds of patients with early behavioural disturbances, residual emotional and cognitive impairments were seen 1 year after injury. This study suggests that behavioural disturbances in the early phase after injury are related to frontotemporal lesions and lends support for the view of the existence of a separate profile of patient behaviour in mild-to-moderate head injury.