Results in 23 patients with significant craniocerebral trauma (Glasgow Coma Scale less than or equal to 10) and displaced acetabular fracture requiring surgery were reviewed after a minimum follow-up of 1 year. Despite a postoperative anatomic reduction in all but one case, clinical outcome for these hips was poor, with an average Harris hip rating of 59. Patients older than 40 years had a significantly poorer outcome than did younger patients (p = 0.004). Postoperative problems occurred in 70% of patients (n = 16); the largest portion of these represented symptomatic heterotopic bone, which occurred in 61%. None of the four patients who had an anterior ilioinguinal surgical approach had symptomatic heterotopic ossification. The average Glasgow outcome score was 3.9 out of 5, and 20 of the 23 patients, despite a prolonged convalescence, were able to return to independence and self-care. The authors conclude that patients with combined significant craniocerebral trauma and an operatively managed displaced acetabular fracture are likely to have compromised hip function despite a well-executed osteosynthesis. This was especially true for those patients over age 40 in this series. The authors suggest that if the fracture pattern permits it, the operative management of the acetabular fracture in these patients be by an anterior ilioinguinal approach, so as to minimize the formation of heterotopic bone.