Parameters of bone mass in the upper end of the femur--the thickness of the calcar femorale and the pattern of the trabeculae--were evaluated in preoperative films of patients who had undergone total hip replacement. Patients with primary coxarthrosis rarely showed signs of osteoporosis; on the contrary, one of the parameters of bone mass was above average in the coxarthrosis cases. However, there was no difference, in the preoperative films, between hips that later went on to show signs of mechanical loosening of the stem prosthesis and hips that remained intact in this respect.