The survival time of mice in 6 atmospheres of O2 was about 40 min. The avg. survival times were prolonged 12, 22, 34, and 146 min., respectively, when the mice were irradiated (8800r) 30, 48, 72 and 84 hrs. previously. Ten of 30 irradiated mice died between 72 and 84 hrs. Anorexia may have contributed to the observed protection.