[en] In comparison with the effect of radiations, hypoxic cells were more thermolabile, and decrease in pH elevated the fatality by heat. As for the sensitivity in the cell cycle, the S phase was resistant against radiations, but sensitive against heat. Cells under growth showed low radiosensitivity in the non-proliferating phase, but showed a reverse relation by heat. Some chemical compounds with a SH group increased heat-sensitibity, as did radiations. Injury generally occurred and was completed in the same cell cycle. The interval between injury and recovery was 9 hr. for G1 phase cells and 18 hr. for S phase cells. Target agents are unknown, but protein and its analogues have been postulated. Combination with radiations brought sublethal to lethal injury of non-synchronized culture cells and showed a synergistic-totalling effect in animal studies. Radiosensitization by heat was pronounced only in tumors, and the optimal interval of treatment was 3 - 4 hr. The temperature of normal tissues stopped rising at about 43₀C, but the intratumoral temperature continued to rise. Tumor regression was observed in cases of marked thrombocytopenia which occurred after thermal treatment. (Chiba, N.)