Treatment of the femoral head necrosis with severe extensive collapse in young adults and adolescents are still challenging. We thought preserve the joint and bone stock were important factor for the treatment of femoral head necrosis in young patients. We reviewed the posterior rotational osteotomy for younger patients with severe osteonecrosis. The advantages of posterior rotational osteotomy are; the necrotic area is moved to non-weight bearing portion. The posterior column artery is shifted medially without vascular damage by rotation. Postoperative uncollapsed anterior viable areas are moved to the loaded portion below the acetabular roof in flexed positions. Eighty five hips of 66 young adults (less than 50 years old, mean age; 31 years) with extensive necrosis treated by posterior rotational osteotomy were reviewed with more than 5 year follow up with a mean of 9 years. Results of 13 hips of 12 adolescents (mean age; 14 years) with extensive collapsed necrosis treated by this procedure were also studied with a mean of 6.5 years. A mean degree of posterior rotation was 121. Recollapse was prevented in 77 hips (91%) of adults, and all 13 hips of adolescents on final AP radiographs. Collapsed lesion was remodeled well and resphericity of the postoperative transferred medial collapsed femoral head on final AP radiographs was observed. However, some of the cases were out of indication of the joint preserving procedure showing extensive lesion. In these cases, we performed the MAYO conservative stem for preserving bone stock. Radiological results of 26 hips with osteonecrosis treated by MAYO stem (mean age 42 years, minimum 5 year follow-up. mean; 6.7 years) showed that 2 mm subsidence in one, osteointegration of zone 2, 6 in 93%, no entire lucent line. No hips were revised for late loosening associated with osteolysis. CT imaging indicated that spot welds of zone 2, 6 were found in 100ï¼ï¿½, stress shielding of zone 1, 5 (23.5ï¼ï¿½). These operations were useful particularly for younger patients.