As the unipolar endoprosthesis showed marked acetabular wear, many researches were performed to find a solution to reduce acetabular wear. Bipolar endoprosthesis, which is known to have motion between two components as well, is widely being used currently. Nevertheless, joint space narrowing used to be found even in bipolar endoprosthesis as time goes by, which resulted in total joint replacement. Clinical and radiological evaluation were made on 2 kinds of implants surgery after more than 1 year follow up, and following results were obtained; 1. Unipolar prosthesis was applied in 12 patients whose average age was 62 years 6 months, and bipolar prosthesis was performed in 33 hips with average age of 57 years 3 months. 2. The disesses of hip were AVN in 18 cases and femur neck fracture in 27 cases. 3. The average of Harris hip score in unipolar group was 47.4 points preoperatively and 78.3 points postoperatively. And in bipolar group it was 50.6 points preoperatively and 84.2 points postoperatively. 4. Joint space narrowing was 0.41mm/year in average in unipolar group and 0.24mm/year in bipolar group.