Socket-cup arthroplasty gives a painless hip and allows a sufficient range of motion for the daily activities of the average patient. Arthrodesis and total hip replacement are clearly possible in the cases in which the operation is a failure. The procedure therefore is relatively conservative. There are 2 major causes of failure. One is atrophy and necrosis of the femoral head and neck covered by the cup. The other is loosening between the acetabular bone and cement in dysplastic hips. The results of clinical trials with socket-cup arthroplasty were disappointing. Reoperation by total hip replacement between 1--5 years after implantation (mean 3 years) was required for 7 of 12 cases. Failure was associated with fracture of the femoral neck secondary to osteonecrosis in one hip and with the loosening of the acetabular socket in 6 hips. To overcome these difficulties, improvements in materials, design and surgical procedure are necessary. The indication for the present designs and materials for socket-cup arthroplasty should be strictly limited.