Totally, 28 consecutive patients with nontraumatic osteonecrosis of the femoral head were included in a prospective study of the clinical and radiographic results of core decompression. One patient (one hip) was lost to follow-up. Preoperatively, the stage according to Ficat (1985) was assessed by plain radiography and scintimetry. After 1-2 years, hip replacement had been performed in 4/11 Stage 1, 7/11 Stage 2, and 4/7 Stage 3 hips, while the remaining 12 hips were judged satisfactory. We conclude that the outcome of core decompression for nontraumatic necrosis of the femoral head is unpredictable.