The results were reviewed for 259 patients who had open reduction and internal fixation of 262 displaced acetabular fractures within twenty-one days after the injury. Two hundred and fifty-five hips were followed for a mean of six years (range, two to fourteen years) after the injury; the remaining seven, which clearly had a poor result, were followed for less than two years. According to the classification of Letournel and Judet, associated fracture types accounted for 208 (79 per cent) of the fractures, with both-column fractures being the most common type (ninety-two hips; 35 per cent).Two hundred and fifty-eight hips were operated on with a single operative approach (Kocher-Langenbeck, ilioinguinal, or extended iliofemoral). The four remaining hips were operated on with a Kocher-Langenbeck as well as an ilioinguinal approach.The reduction was graded as anatomical in 185 hips (71 per cent). The rate of anatomical reduction decreased with increases in the complexity of the fracture, the age of the patient, and the interval between the injury and the reduction.The over-all clinical result was excellent for 104 hips (40 per cent), good for ninety-five (36 per cent), fair for twenty-one (8 per cent), and poor for forty-two (16 per cent). The clinical result was related closely to the radiographic result. The clinical result was adversely affected by associated injuries of the femoral head, an older age of the patient, and operative complications. It was positively affected by an anatomical reduction and postoperative congruity between the femoral head and the acetabular roof. Osteonecrosis of the femoral head was noted in eight hips (3 per cent), and progressive wear of the femoral head was seen in thirteen (5 per cent). Subsequent operations included a total replacement of seventeen hips (6 per cent), an arthrodesis in four (2 per cent), and excision of ectopic bone in twelve (5 per cent).These findings indicate that in many patients who have a complex acetabular fracture the hip joint can be preserved and post-traumatic osteoarthrosis can be avoided if an anatomical reduction is achieved. An increase in the rate of anatomical reduction and a decrease in the rate of operative complications should be the goals of surgeons who treat these fractures.