In a retrospective study the long-term results of conservative treatment of acetabular fractures has been evaluated. From 1967 through 1983, 79 patients with 81 fractures of the acetabulum were treated. The fractures were classified according to Judet and Letournel (1). Out of these 79 patients 83% had multiple injuries. The mean Injury Severity Score was 34 (9-75). Follow-up examination was performed in 55 patients. Partial avascular necrosis of the femoral head appeared in 11%. Fractures without dislocation had all a good prognosis. Fractures with dislocation, where the anterior column was involved, had a relative similar prognosis. In 79% of patients, where the dorsal column or roof of the acetabulum was involved, had a moderate or bad result. We conclude that no optimal result can be expected, when in dorsal column or acetabular roof fractures the reposition achieved by conservative treatment is insufficient. In these cases operative reposition and fixation should be considered.