A total hip arthroplasty was performed, with use of the anatomic medullary locking hip system, in 223 consecutive, non-selected hips in 215 patients. The mean age of the patients at the time of the operation was fifty-five years (range, sixteen to eighty-seven years). Twenty-one patients (twenty-two hips) were lost to follow-up and twenty-seven patients (twenty-seven hips) died less than ten years postoperatively. The remaining 167 patients (174 hips) were followed for a minimum of ten years (mean, eleven years; maximum, thirteen years). There were twenty reoperations involving a component. The rate of survival at twelve years was 0.97 +/- 0.02 (mean and standard error) for the stem and 0.92 +/- 0.03 for the cup. Patients who had osteolysis were younger than those who did not have osteolysis (mean age, forty-seven compared with fifty-six years; p < 0.01). Similarly, patients who had a reoperation were younger than those who did not have a reoperation (mean age, forty-six compared with fifty-four years; p < 0.01). The radiographic appearance of progressive wear that, in our opinion, was severe enough to cause the femoral head to completely penetrate the polyethylene liner was the most frequent reason for reoperation.