Acetabular fracture is a severe injury associated with other body injuries. they result in permanent disability due to management difficulty and its complications such as traumatic arthritis, avascular necrosis of femoral head, etc.. In order to restore excellent function of hip joint, anatomic reduction and secure internal fixation followed by early mobilization are neccessary. We analysed 21 patients who were diagnosed as type A1 acetabular fracture from Jan. of 1991 to Dec. of 1996, and compared the functional results of conservative treatment method with that of surgical treatment method. The results were as follows. 1. Conservative management was done at 8 cases, and surgical management was done at 13 cases with open reduction and internal fixation. 2. The functional result by Goodwin criteria was all satisfactory in conservative reatment method and 12 cases(92%) in surgical treatment method. 3. Associated injuries were found in 18 cases, among them pelvic bone fracture was the most common fractured site and knee ligament injury was the most common soft tissue injury. 4. In the cases of larger acetabular fragment or in the presence of associated injury and instability after closed reduction, faster rehabilitation was achieved by starting early range of motion exercise and weight-bearing after surgical treatment than classical conservative treatment.