From 1972 until 1988, transtrochanteric rotational osteotomy was used to treat 474 hips in 378 patients with idiopathic and steroid-induced osteonecrosis of the femoral head. Two hundred twenty-nine of 295 hips with anterior rotation and follow-up periods ranging from three to 16 years had excellent surgical results (success rate, 78%). Outcome was chiefly dependent on the ratio of transposed intact posterior articular surface to the acetabular weight-bearing area after osteotomy. This relationship suggested that the transposed intact area should occupy more than 36% of the acetabular weight-bearing area by adequate rotation and intentional varus position in addition to rotation, especially for extensive lesions. Salvage operations, such as total hip arthroplasty, were performed on 18 hips, of which ten hips were cases of either relative indication for extensive lesions in young patients or other misindications for rotational osteotomy. Four hips sustained neck fracture, including three hips after 180 degrees of posterior rotation; two hips were complicated with avascular necrosis, and another two hips developed osteoarthrosis. Histologically, femoral heads with osteoarthrosis removed at the time of salvage operation showed complete healing of the necrotic lesion. The overall findings indicate that healing of the necrotic lesion of the femoral head may be brought about by rotational osteotomy if it spares the vulnerable site from the brunt of mechanical stress.