1. A total of 120 Moore's arthroplasties in 111 patients were reviewed one to nine years after operation.

2. There was striking reduction in the severity of pain in 105 out of the 120 hips reviewed. Range of movement was improved in most patients but the degree of independence was improved less often. The reasons for this are discussed.

3. We draw the following conclusions regarding the place of Moore's arthroplasty. Firstly, it was a natural step in the evolution towards total hip replacement, an operation which promises to give more complete relief of symptoms and which seems likely to replace Moore's arthroplasty as the treatment of choice in osteoarthritis of the hip in the elderly. Secondly, Moore's arthroplasty is still a rational procedure for the treatment of degeneration if the acetabulum is not involved—for instance, in idiopathic avascular necrosis of the femoral head. Thirdly, it is certainly a valuable operation for some cases of recent fracture of the femoral neck. Avascular necrosis of the femoral head after trifin nailing can be satisfactorily treated by Moore's arthroplasty, particularly in the early stages before the acetabulum becomes involved. Finally, Moore's arthroplasty gave many fairly elderly patients considerable relief of pain at a time when nothing better was available. Much of the relief afforded has proved to be lasting, but deterioration sometimes occurred with time. In the few patients whose deterioration amounted to failure a definite cause for the failure was found. In the majority the deterioration was slight, and it seems likely that the operation will last most of these elderly patients for the rest of their lives.