The records of 496 adult patients who sustained severe injuries to the head were reviewed retrospectively in order to reveal the incidence and location of heterotopic ossification. All traumatized joints were excluded from the study. Clinically significant heterotopic bone causing pain and a decrease in the range of motion of the adjacent joint was identified in 100 joints in fifty-seven patients (11 per cent). All fifty-seven patients had some residual spasticity, although the spasticity was not always present about the involved joint. Twenty-seven patients had monoarticular involvement while thirty patients had involvement of more than one joint. Forty-four hips, twenty-seven shoulders, twenty-six elbows, and three knees had heterotopic ossification. Complete ankylosis (16 per cent of all joints) developed in eight elbows, six hips, and two shoulders.