Injuries are the leading cause of death among American Indians. An epidemiologic study was conducted on the Hopi reservation to assess the incidence, circumstances, and outcome of injuries. The incidence of hospitalized or fatal injuries during 1979-1980 was 12 per 1,000 persons per year, with the highest incidence in the age group of those older than 84 years. Overall, falls, motor vehicle crashes, self-inflicted injuries, and assaults were the leading causes of injuries. Suicides and crashes were the leading causes of death. The 15- to 29-year age group, which constituted only a quarter of the population, accounted for 46% of all injuries. This age group had especially high rates of self-inflicted injuries, crashes, and assaults. Injury problems of special importance to the Hopis included single-vehicle rollover crashes, falls from pickup trucks, falls from mesas and pueblo roofs, and suicide attempts in jails.