Intravenous injections of 2.8, 0.90, 0.30 and 0.096 µc Pu239/kg induced 7/9, 12/12, 12/12 and 7/8 bone cancers in adult beagles. The average accumulated rads to the skeleton varied from 326 ± 70 to 6470 ± 1590. The osteogenic sarcomas appeared later at lower dose levels and absorbed skeletal radiation doses. Multiple primary osteogenic sarcomas varied from 0 to 7 tumors/dog. Sixty-eight per cent of the tumors originated from the spongiosa of extremities (36.7 per cent) and the vertebral column (32.7 per cent). A total of 93.9 per cent (92/98) tumors arose from spongy bone, while only 6.1 per cent (6/98) originated from cortical bone. The anatomical distribution of osteogenic sarcomas differed for each dose level. A fibrosarcoma and a squamous cell carcinoma involving the skeleton were detected in the 0.096 µc/kg group. Radiochemical analyses of individual bones showed extreme variation in plutonium concentration from bone to bone and within individual bones. The skeleton exhibited extensive gross tissue damage in the higher dose levels, while only isolated empty lacunae in trabeculae and canal plugs and loss of osteocytes in cortical bone were observed in the 0.096 µc/kg group. The relationship of gross tissue damage to bone tumor production is discussed.