An end-result analysis is presented of thirty-nine mold arthroplasties performed at the Massachusetts General Hospital between 1945 and 1965 in thirty-eight consecutive private patients for arthritis of the hip following fractures of the acetabulum or dislocations of the hip.

Of the nineteen unilateral cases in the second half of the series, sixteen were rated good or excellent. Results in the second half of the series were significantly better statistically than those in the first half of the series. Possible reasons for this improvement are discussed.

No significant deterioration occurred with the passage of time. Among the thirty-nine hips, three revisions were required. One patient had postoperative sepsis after arthroplasty. Four patients who had had intra-articular sepsis prior to arthroplasty showed no evidence of sepsis postoperatively.

Factors influencing the choice between hip fusion and hip arthroplasty in these cases are presented.

A new system for rating hip function is proposed and is compared with the systems of Larson and Shepherd.