The clinical and radiological results of bipolar hemiarthroplasty(BH) and total hip arthroplasty(THA) were compared by analyzing 12 patients of bilateral osteonecrosis of the femoral head; all were treated with cementless THA for one hip and cementless BH for the other within the same year, by the same surgeon. The average duration of follow-up was 70 (39-104) months. At postoperative 2 years, all patients were satisfied with both sides. Subjectively, four patients felt better off with THA than with BH. The difference was not significant, and between the two groups there was no statistical difference in the Harris hip score or pain score. At the last follow-up, five patients were happier with THA, and two with BH. Periprosthetic osteolysis was identified in seven cases of THA and one of BH; its extent was greater in THA than in BH cases, and in three of seven THA cases, severe periprosthetic osteolysis required further surgery. In conclusion, subjective patient satisfaction was slightly better with THA than with BH, but the survival rate in BH cases was higher than in those of THA. The main cause of failure was periprosthetic osteolysis, which was more frequent and severely complicated in THA than in BH.