PURPOSE: To analysis clinical and radiological results of operative treatment of displaced acetabular fractures and establish the guideline for the operative treatment of displaced acetabular fracture with the analysis of the clinical and radiological results. MATERIALS AND METHODS: A clinical analysis was performed on 36 patients with displaced acetabular fractures who had been operated on and followed for minimum 1 year period from January 1993 to December 1998. Clinical outcome was analyzed clinically by Harris hip scoring system and radiologically by Matta's roentgenographic grading system. RESULTS: According to Letournel's classification, we had 25 elementary fractures(69%) and 12 associated fracture(31%). Among the elementary fractures, the posterior wall fracture was the most common type(17 cases, 47%) and both column fracture was the most common type among associated fractures(5 cases, 11%). Surgical approaches were 22 Kocher-Langenbeck, 8 extended iliofemoral, 3 triradiate transtrochanteric, 3 ilioinguinal. The mean duration of follow up after the operation was 2.2 years (range, 1 to 7 years). Among thirty six patients who had followed up more than one year, the satisfactory results were achieved in 27 cases (75%) on clinical grade and 26 cases (72%) on radiographic grade. The complications were developed in 20 cases out of 36 cases including posttraumatic arthritis 7 cases, heterotopic ossification 4 cases. CONCLUSION: In the majority of the displaced acetabular fractures, accurate open reduction and internal fixation was recommended. It seems that the satisfactory operative reduction of the fracture is the factor that correlates with a satisfactory clinical result according to our study. Therefore in the surgical treatment of the acetabuluar fractures, it is essential to achieve an anatomical reduction and firm fixation by fully understanding the pathologic anatomy and by choosing an appropriate approach and fixation device.