Severe head injuries often lead to serious medical and socioeconomic sequelae. The incidence rate indicated in other studies shows a wide variation due to differences in selection criteria. Based upon an unselected population, the incidence of severe head injury was calculated and the surviving patients were interviewed and clinically examined 3 years after the accident in order to describe the course, rehabilitation and psychosocial sequelae after severe head injury. Retrospectively we collected 80 patients living in the canton of St. Gallen who had a severe head injury requiring hospitalization in 1987, indicating an incidence of 20 per 100,000 inhabitants. 22 (28%) of these patients died as a consequence of the head trauma. The best predictor was the Glasgow coma score at admission, which showed a highly significant direct correlation with survival rate. Regarding the degree of impairment of survivors the duration of posttraumatic amnesia was the best predictive parameter. Of the 45 patients controlled 3 years after the head trauma only 11% were severely impaired in daily activities. 79% of the patients who were gainfully employed before the accident were working full- or at least part-time. However, only 3 patients (7%) were absolutely free of symptoms. Most patients suffered from cognitive and emotional deficits. Based on an estimated incidence for minor head trauma of 174 per 100,000 inhabitants, a total annual incidence for all head traumas of 194 per 100,000 inhabitants is calculated, with severe head injury representing about 1/9 of all head injuries.