71 patients undergoing primary hip arthroplasty due to osteoarthritis were randomized to receive either conventional metal-on-metal total hip arthroplasty or hip resurfacing arthroplasty. The purpose of this study was to determine the impact of the two procedures on bone mineral density of the femur over a period of 3 to 5 years. Periprosthetic bone densitometry in five regions of the proximal femur and incidence of femoral neck narrowing were measured through DXA scans. The results indicate that hip resurfacing arthroplasty significantly preserved bone stock in the proximal femur, particularly in the calcar region, when compared to the results of total hip arthroplasty.