In treating fractures of the femoral neck, it is necessary to choose between techniques that conserve the femoral head in anticipation of its survival and union and techniques in which the head is sacrificed and replaced with a prosthesis. The latter techniques permit much earlier weight-bearing. They were tried in 51 patients, one of whom had bilateral fractures, so that 52 prostheses were used. The average age of the patients was 74 years. The bilateral fractures occurred in a man aged 92; he resumed walking the second day after insertion of the prostheses. Similar good results were obtained in many other patients as well, but the hazards of the operation were manifest, and longer periods of observation will be necessary in order to preclude the possibility of pain, arthritic degeneration, and other complications in later years. At present the insertion of a hip prosthesis as the primary treatment for a fracture of the femoral neck is not advised in patients under the age of 70 except under special circumstances.