For reappraisal of total hip arthroplasty (THA) in the treatment of nontraumatic osteonecrosis (ON) of the femoral head, 29 hips in 23 patients with ON were surveyed in a comparison with 63 osteoarthritic (OA) hips treated in the same manner during the same period; the hips were selected according to the same criteria. The 29 ON hips were followed for an average of seven years. Comparing the ON and OA groups, the patient profiles were similar, except for weight and sex. For the ON group, hip scores according to the Merle D'Aubigne system (18 points for a normal hip) were improved from 9.8 preoperatively to 14.3 at the latest survey. However, 14 hips (48%) presented unsatisfactory clinical results, and roentgenologically all showed aseptic component loosening. Such a failure rate was higher than that for the OA group (33%); similarly, femoral component loosening occurred more frequently in the ON (28%) than in the OA group (5%). Based on the analysis of the patient profiles, Stage 3 ON at surgery, bilateral occurrence of the disease and bilateral THA could have caused such a failure in the ON group. In addition, most of the hips with component loosening showed histologic evidence of extensive bone necrosis within the resected femoral head. ON is a high-risk disease in terms of the long-term durability of THA, the failure of which seems to be mainly caused by extensive necrosis.