Between 1978 and 1984 373 Müller prostheses have been used in treating post traumatic lesions of the hip joint. Three groups of patients were concerned: elderly people with fresh fractures of the femoral neck; late sequels of femoral neck fractures; late sequels of acetabular fractures. The follow-up period ranged from 18 months to 8 years. Special attention was brought to late mechanical problems and the final functional status of the patients. We could conclude that: 1. Three years after surgery about 50% of the survivors were still in a good functional condition. After 5 years, this number decreased to 35%. 2. Total prosthesis with "banana formed" stem has to be abandoned. After five years signs of loosening were present in nearly all the cases. The functional results of the straight stem prostheses were significantly better. 3. Old people in good general condition with a fresh fracture of the femoral neck are better of with a total hip replacement than with a hemiarthroplasty. 4. Late sequels of acetabulum fractures present a more complex problem. Maybe a total hip arthroplasty is not always the best final solution.