Acetabular fractures are relatively uncommon, but frequency is becoming increasingly with the increase of autombile accident. Undisplaced acetabular fractures have a good prognosis, but major displaced acetabular fractures have always given rise to difficulty and have a problem if fractures are not accurately evaluated, classified and reduced anatomically. The principles of treatment are to restore the fractured acetabulum to its normal anatomy, to maintain and restore the function and accordingly early joint motion to promote healing and to prevent joint adhesion. However, the treatment of displaced fracture of acetabulum has been controversal. Judet et al, Pennal and Matta et al advocated open reduction and internal fixation for displaced fracture of acetabulum. But, Watson-Jones and Crenshaw reported that, if closed reduction such as traction was used, good result could be obtained. The authors studied the sex and age distribution, classification according to roentgenographic findings, associated injuries, methods of treatment and prognosis of total hip replacement for traumatic arthrits in complicated patients among 63 patients who were admitted to the department of Orthopedic Surgery of Chonbuk University hospital under diagnosis of acetabular fracture. The results were as follows, 1. The prevalant age was third decade and the cause of injury was traffic accident in the majority. 2. The most common type of fracture was posterior wall fracture and the second was transverse fracture by Letournel classification. 3. The complications were posttraumatic arthritis, ectopic ossification, peroneal nerve palsy and wound infection. 4. The prognosis of the total hip arthroplasty for complicated traumatic arthritis was relatively poor than others. 5. Satisfactory results by clinical criteria(by Postel) of operative treatment were 71% and conservative treatment, 46%. In the majority of displaced acetabular fractures, open reduction and internal fixation was recommended. If surgery is attempted, it is essential to achieve an anatomical reduction and firm fixation by fully understanding the pathologic anatomy and by choosing an approapriate approach and fixation device.