Acetabular fractures are relatively uncommon, but when they occur they often result in permanent disability due to management difficulties. Undisplaced acetabular fractures have a good prognosis but major displaced acetabular fractures have always given rise to difficulty and concern during treatment and have a variable prognosis in different reports. In order to restore excellant function to a displaced acetabular fracture, anatomic open reduction and secure internal fixation followed by early mobilization are neccessary. And in order to approach fracture of acetabulm safely and with maximum ease, it is neccessary to understand the pathologic anatomy. The authors studied the sex and age distribution, clssification according to roentgenographic findings, associated injuries and methods of treatment of 49 patients who were admitted to the department of orthopedic surgery of our hospital from January, 1976 to June, 1981 under the diagnosis of acetabular fracture. The results of treatment of 31 patients who were followedup over a 6month period were as follows: 1. The mean age was 37 years, the range being from 17 to 71. 2. The most common cause of injury was traffic accidents (38 cases: 77.6%) which was followed by falls from heights (5 cases;10.2%). 3. Thirty cases were treated by conservative mea ures and 19 by surgery. The results were as follows: Excllent-10(32.3%), Good-14 (45.2%), Fair-6(19.3%), Poor-1 (3.2%), 4. The one case that had a poor result was a “T” shaped fracture with a central dislocation, which was impossible to reduce surgically due to severe comminution. 5. If the grossly displaced fragments are present they should be reduced and fixed surgically. But only if anatomical reduction and secure internal fixation is possible, surgery should be done. With a severely comminuted fracture, medial wall fracture, or central fracture-dislocation, surgical treatment is difficult therefore conservative treatment is better. 6. It is of great help to have various methods of roentgenography, conventional tomography, and computed axial tomographic scan in order to understand the pathologic anatomy of complicated acetabular fractures. 7. If surgery is attempted, it is essential to achieve an anatomic reduction and firm fixation by fully understanding the pathologic anatomy and by choosing an appropriate approach and fixative device.