GAMMA DOSE RATES AT RONGELAP ATOLL, 1954-1963 ABSTRACT Rongelap Atoll was contaminated with fallout from a thermonuclear device on March 1, 1954. 3.5 rfhr to 35 r/hr. Gamma-dose rates on D + 1 ranged from Until 1959 the decline of gamma-dose rates measured in the field followed the theoretical decay of mixed fission products from y73° calculated by Miller and Loeb. The reduction of gamma dose rates to approximately half the predicted levels in 1959~63 probably reflects the downward movement of the long-lived gamma-emitter cs3?7 in the soil. Redistribution of fallout had little effect on gamma dose rates except in the intertidal zone. It is concluded that predicted gamma dose rates from fallout based on the theoretical decay curve of radionuclides from fission of U than actual levels. 235 would tend to be equal to or greater