Fractures of the acetabulum are relatively uncommon, but because they involve a major weight bearing joint in the low extremity, they assume great clincal importance. The principle of management for this fracture is as for any other displaced intra-articular fracture, nsmely that anstomical reduction is essential for good long term function of the obtained by closed means, but more often, open reduction followed stable internsl fixation allowing early active or passive motion will be required. In the past, the achievement of this ideal, that is anatomical reduction, has been difficult because technical problems such as those caused by complicated anatomy, difficulty with surgical exposure, severe comminution in many cases, and major associated injuries. We classified the acetabular fractures of 71 patients with 72 hips from 1980 to 1987 and clinical analysis was performed on 51 hips allowing the possible follow-up evaluation beyond the 12 months. Following results were obtained. 1. The most common associated injury was the pelvic bone fracture(25.5%). 2. The most common types of fracture on each classification were posterior wall fracture in Letournel(37.5%), posterior acetabular fracture in Rowe & Lowell(42.3%), central fracture- dislocation without involving of weight bearing dome of acetabulum in Carnesale(23.9%). 3. According to calssification method, the interpretation for characteristics of fracture type and frequency of acetabular fracture was very different each other. 4. The Leournels classification was relatively simple and could contain with many types of fracture and was helpful to determine the index of treatment. 5. The prognosis of linear undisplaced fracture and posterior fracture was better than acetabular medial, superior and bursting fracture in both conservative and operative treatment. 6. The posterior wall fracture with widely displaced fracture or joint instability, acetabular dome fracture, intraarticular fragment was absolute indication for operative treatment. 7. The treatment result and prognosis was influenced to the accurate classification of fracture type, anatomical reduction and rigid internal fixation.