THE CLINICAL recognition of aseptic necrosis of bone is based largely on the appearance of changes in the roentgenogram, and these of necessity must be the result of slowly developing factors on one of the resisting tissues of the body—bone. Death of bone tissue without evidence of infection has been described in various regions of the body in both childhood and adult life, and the factor or factors affecting its prevention or progress are of practical value. The bone infarct in the diaphysis may be asymptomatic, but whenever the pathologic process involves one of the articular surfaces, it will give rise to limitation in the joints and produce severe disability. In childhood Freiberg's disease, Perthes' disease and Köhler's disease are all representative of a localized aseptic necrosis. In the adult the development of aseptic necrosis in the head of the femur following a traumatic dislocation or a fracture of the