his essociates=>/ it appears that completely effective functioning is not likely for persons who have received a dose in the lethal range. On this basis, the following generalization may be applied: within the first week, all personnel subject to radiation with an R,fe equal to or greater than the 5% lethal dose in 30 days are considered sick and should not be used for work of any kind. Operation CASTLE Experience. The first shot of the CASTLE test series was fired 1 March 1954 on a reef at Bikini atoll, with a total energy yield of 15 MI, Changing weather conditions arotnd and after shot time resulted in deposition of a portion of the fall-out pattern from this shot over the populated atolls of Rongelap, Rongerik, and Uterik, although the heavier contaminated axis of the pattern lay north of these island _ groups. The populated islands of these atolls were evacuated promptly, but not before a group of natives on Rongelap had received an estimated whole-body dose of gamma radiation above 80 kev in the neighborhood of 175 roentgens. A small group of American service men on Rongerik re- ceived an estimated 95 roentgen whole-body dose, and a native group from Utirik about 15 roentgens before being evacuated. An island sur- vey team monitored the islands of these atolls carefully over a period of several days beginning on the seventh day after the shot, making a valuable documentation of the fall-out intensities in the living areas involved, as well as on neighboring wpopulated islands. As a result of careful observations made upon the exposed individuals and of analyses of the related physical data obtained from subsequent shots of the CASTLE series, a wealth of pertinent data on the radiation hazards of fall-out is now at hand. These data indicate that careful consideration must be given the external hazard problems associated with beta and gamma radiation from radioactive fall-out in 23/ Trun, B.F., et al., Clinical Observations Upon the Response of the Burro to Large Doses of External Whole Body Gamma Radiation, Auburn Veterinarian, 8, 1952. 82