Since 1983, the transtrochanteric rotational osteotomy has been performed in 38 hips of 36 patients for the nontraumatic avascular necrosis of the femoral head at the department of orthopaedic surgery of Seoul National University Hospital. Out of them, 26 hips(18 cases of Sugioka grade I and 8 cases of Sugioka grade II ) were followed up for more than 1 year. The average period of follow-up was 3 years and 5 months(range, 1 year and 2 months to 7 years). These cases include 3 cases of failure before 2 years after operation. Overall, the result was satisfactory in 20 cases(77%)out of a total of 26 cases(success in 18 cases(69%)and good in 2 cases(8%)). The results of the grade I lesions(14 cases of success and 1 case of good result out of 18 cases) were better than those of the grade I lesions(4 cases of success and 1 case of good result out of 8 cases). Complications occurred in 5 cases. These include an ectopic ossification, a stress fracture of the neck, a nonunion of the osteotomy site, a nonunion of the greater trochanter and a delayed union of the greater trochanter. There were 6 cases of failure. For the 4 cases of them, hip replacement arthroplasy was performed. The MRI images axial to the longitudinal axis of the femoral neck gave excellent information for the operation.