PURPOSE: The purpose of operative treatment in acetabular fracture is to restore anatomically the disrupted joint surface and prevent post-traumatic arthritis. We analysed the relationship between the types of the fracture, its location, reduction state with the development of post-traumatic arthritis and hip joint function in postoperative period. METHOD & MATERIAL: A clinical analysis was performed on 14 patients, excluding patients with anterior & posterior wall fracture, with displaced acetabular fracture who had been treated by open reduction and internal fixation. All patients had been followed for minimum 1 year in our department from May 1989, to February 1999. RESULTS: The type of acetabular fracture was not correlated statistically with posttraumatic arthritis and Harris hip score. The reduction state of acetabular fracture was significantly correlated with post-traumatic arthritis and Harris hip score. The antomic location of acetabular fracture was not correlated statistically with post-traumatic arthritis but correlated with Harris hip score. CONCLUSION: Anatomic reduction is more significant factor in postoperative outcome of acetabular fracture than the type of fracture and the anatomic location of fracture.