1. Results are reported for cases of advanced and recurrent sarcomas of bone and soft tissues treated with 4 mev. roentgen rays under conditions of circulatory arrest produced by a tourniquet and in hyperbaric oxygen at 4 ATA, respectively.2. The treatments have been administered to an initial series of 60 cases. Distant metastases were demonstrated in 19/60 (32 per cent) before treatment and a majority of cases treated were recurrent after surgery or roentgen-ray therapy.3. The crude cumulative survival rate at 12 months differed for the two modalities, being 12/20 (60 per cent) in the tourniquet group and 7/22 (34 per cent) in the hyperbaric group, respectively. The difference is attributable to the stage of disease treated in the various groups.4. Regression and sterilization rates of tumors produced were high with both anoxic and hyperbaric techniques, a pessimistic estimate of 70 per cent tumors resolving after the treatments which produced both acceptable levels of tissue reactions and tolerance. Ab...