OBJECTIVE To research on the conservative methods used to preserve the femoral head of patients with osteonecrosis of the femoral head. METHODS In these series surgical procedures the osteonecrotic lesion was removed and various vascularized bone blocks or periosteal flaps with its nutrient vessels were transferred to regain sphericity of the femoral head and reinforce the sequestrum. The current study assessed 1005 patients (1226 hips) operated on from 1989 to 2002 with an average follow-up of 5.1 years (range, 1.5-15 years). The mean age of the patients was 37.4 years (range, 17-65 years). RESULTS Sixty-one hips (57 patients) had conversion surgery to a total hip arthroplasty because of progressive collapse or severe pain, or both. In the patients without failure, postoperative Harris hip score improved significantly. Of the 1174 reconstructions that were in situ, 1041 (89.4%) were clinically successful, and 878 (75.4%) were radiologically successful. In relation to the stage of necrosis according to the classification system of Ficat and Alert, good results were achieved in 95.3% of the patients with stages II disease, 87.9% with stages III and 60.8% with stages IV. CONCLUSIONS Conservative methods of vascularized bone block or periosteal flap transfer should be considered in active symptomatic patients to preserve the femoral head. In addition, the earlier the stages of the disease the better outcome could be obtained.