The authors present a consecutive series of 38 arthroplasties for osteoarthrosis secondary to hip dysplasia. All arthroplasties were performed by a single surgeon using Mittelmeier II (Autophor, Osteo AG, Selzach, Switzerland) ceramic cementless components. Crowe grades of subluxation were 60% grade I, 16% grade II, 12% grade III, and 12% grade IV. In all cases, the acetabular component was seated in the true acetabulum. The mean follow-up period was 75 months (range, 40-122 months). By the time of review, six hips (16%) had required revision for aseptic loosening, mainly of the femoral component. Good or excellent results were achieved in only 63% of the patients. In the group of surviving arthroplasties, the median Charnley hip scores before surgery were: pain, 2; movement, 3; and walking, 3. After surgery, the scores were: pain, 5; movement, 5; and walking, 6. All improvements were significant. The mean postoperative Harris hip score was 84. Poor scores were associated with contralateral hip disease (2 cases) and spina bifida (2 cases), significantly affecting function. The Autophor prosthesis can produce satisfactory results in some of these young patients with hip dysplasia. However, femoral loosening is a major problem and because of this, the authors have since changed to a newer stem design.