It is controversial whether bipolar hemiarthroplasty or total hip arthroplasty should be done for Ficat Stage III osteonecrosis of the femoral head. A prospective comparative study was done using the same cementless femoral components for both procedures. Forty cementless bipolar hemiarthroplasties and 31 cementless total hip arthroplasties were done in 54 patients with Ficat Stage III osteonecrosis of the femoral head. Age, gender, and followup were matched between patients having bipolar hemiarthroplasty and total hip arthroplasty. Treatment with total hip arthroplasty increased the total hip score more than treatment with bipolar hemiarthroplasty. The final pain score especially showed a significant difference between patients who had a bipolar hemiarthroplasty (5.5) and patients who had a total hip arthroplasty (5.9). Thigh pain occurred in four patients (four hips) from the bipolar hemiarthroplasty group and in six patients (six hips) from the total hip arthroplasty group. In the bipolar hemiarthroplasty group, gluteal pain occurred in six patients (six hips, 15%) and groin pain occurred in eight patients (eight hips, 20%). Dislocation occurred in two hips (two patients) in each group. The outer head migrated superiorly in nine hips (nine patients) (23%) from the bipolar hemiarthroplasty group. Because of the incidence of gluteal and groin pain and migration, total hip arthroplasty is a better procedure than bipolar hemiarthroplasty for patients with Ficat Stage III osteonecrosis of the femoral head.