104 patients with advanced unilateral degeneration of the hip undergoing unilateral primary hip replacement were randomized in this study to receive either total hip arthroplasty (THA) or surface replacement arthroplasty (SRA). Radiographs comparing the operated hip with the normal contralateral hip were taken pre and post-operatively. Results indicated that patients in the SRA group had a more precisely restored proximal femoral anatomy than those in the THA group. Significantly more SRA patients were also able to have their leg length inequality restored to within SD 4 mm.