A number of chemical compounds that modify radiation effects are reviewed, with brief report of our own experiments on radioprotective effect of some vasoconstrictive agents and 5-Thio-D-Glucose. Sulfhydryl compounds(-SH group) and some pharmacologic compounds such as CNS depresants, vasoconstrictive agents and autonomic drugs are known to have radioprotective effect in experimental research and in limitted clinical study, whereas oxygen, hallogenated pyrimidines and metronidazole, etc. have radiosensitizing effect. Author experimentally observed some radioprotective effects of angiotensin II, a strong vasoconstrictor, and 5-Thio-D-glucose in mice.