Attention is called to the various roentgenologic manifestations of osteonecrosis. These include a subtle diffuse mottling of the bone, periosteal bone apposition along the femoral neck, isolated patches of sclerosis, irregular discrete rarefactions with fuzzy marginal sclerosis, the " rimsign," the "bite sign," subchondral cortical depression, generalized subchondral fragmentation and possibly acetabular protrusion. The so-called "steroid arthropathy" may in some, if not most, instances represent unrecognized aseptic necrosis. The signs and symptoms of osteonecrosis are non-specific and the clinical diagnosis rests largely with the radiologist. This diagnosis should be considered in patients who have "rapidly developing osteoarthritis," particularly in young individuals and in those who have received steroid treatment. A number of clinical conditions appear to be associated with aseptic bone necrosis but the nature of these relationships and the pathogenesis of the bone lesions are not well understood.