Accurate anatomical reduction of the displaced acetabular fractures has a great clinical importance because acetabulum is related to weight-bearing and their fractures can lead to serious major sequelae. There are controversies and a lot of problems with regard to the management of the displaced acetabular fractures. The purpose of our study is to analyze the clinical results of operative treatment of the displaced acetabular fractures and to establish guidelines for treatment of their fractures. A clinical analysis was performed on 19 patients with displaced unstable acetabular fractures who had been operated on and followed for minimum 1 year period at Asan Medical Center from September 1989 to August 1992. The results were as follows: 1. The most common type was posterior wall fracture according to Letournel's classification. 2. Excellent or good results were obtained in 84% according to Goodwin's assessment method. All of the elementary fracture.s presented excellent or good results, while fair or poor results were observed in some T-shaped fractures or transverse and posterior wall fracture. 3. Complications were observed in 5 cases, including ectopic ossification(2 cases), traumatic arthritis(1 case), avascular necrosis of femoral head(1 case) and deep wound infection(1 case). Those seemed to be related with severe acetabular injury and extensive approach. 4. Kocher-Langenbeck approach was satisfactory for reduction and fixation of posterior column in transverse fracture, while extended iliofemoral approach was necessary for fixation of both column in T-shaped fracture. 5. Reduction of fracture of ilium was prerequisite for reduction of acetabular articular surface. 6. In displaced unstable acetabular fractures, early surgical intervention shich includes accurate anatomical reduction, and rigid internal fixation should be undertaken, and early joint motion should be followed to restore the joint function and to decrease the complication rate.