CT and conventional radiography of the traumatic acetabular fractures are analysed in 31 adult patients inwhom acetabular fractures were demonstrated or suspected on initial radiographs. The results were as follows; 1. Oblique views are useful in demonstration of acetabular columns and acetabular walls, but frequently impossible toperform due to limitation of motion. 2. CT was superior in evaluation of posterior column fracture, two column fracture. 3. CT was also superior in demonstration of the acetabular dome, posterior column, the important components in stability of hip joint. 4. CT reveals hidden loose body, soft tissue injury in plain film. 5. Combined reformations of CT was also useful in evaluation of 3-demensional pathologic anatomy.