One hundred nine Wagner resurfacing arthroplasty acetabular components retrieved at revision surgery were examined for type, depth, and extent of wear at the periphery of the components. Ninety-two components were found to have evidence of peripheral wear caused by impingement of the femoral neck on the edge of the component. The thickness of the wall loss due to this impingement wear was found to be less the farther that measurements were taken from the edge of the component. Thus, when those components with any evidence of impingement wear were analyzed, it was found that significantly fewer components had evidence of impingement at depths of 3 mm and 5 mm in from the edge of the component. It is suggested that future designs of resurfacing hip arthroplasty acetabular components should be at least 3 mm and possibly 5 mm less than a hemisphere. This is likely to lead to less impingement on the femoral neck and therefore less cause for mechanical loosening and less production of wear debris.