The purpose of this study is to analyze the results of treatment of posterior wall fracture of acetabulum, which were treated at our hospital from September 1994 to December 1996. Among 24 posterior wall fractures, 15 cases were confirmed as isolated posterior wall fractures and nine fractures were associated with other acetabular fracture(4 transverse fracture, 3 both column fracture, and 2 posterior column fracture). Clinical follow-up was performed for a minimum of 2 years. The posterior wall fracture was classified according to fracture size(type 1<25%, type 2: 25-50%, type 3: 50-75%, type 4: >75%) and comminution (A: without comminution, B: with comminution, C: impacted) on standard roentgenogram and CT scan. Fourteen among 24 posterior wall fractures were followed for a minimum of 2 years, and the mean Harrif hip score was 91.2. Dislocation of hip occurred in 12 hips(50%). There was no definite difference of Harris hip score in regard to fracture size and comminution of posterior wall. Fractures with posterior hip dislocation had poor result compared with fractures without posterior hip dislocation. Anatomical reduction showed better clinical result than imperfect and poor reductions.