GAMMA DOSE RATES AT RONGELAP ATOLL, 1954-1963 INTRODUCTION Rongelap Atoll, Marshall Islands, was accidentally con- taminated on March 1, 1954 with radioactive fallout from a chermonuclear device detonated at Bikini Atoll some 80 miles to the west. Eighty-two natives residing on Rongelap Island were evacuated and repatriated in June 1957. The atoll, its inhabitants and its economy have been briefly characterized?) , The decline of gamma dose rates resulting from the fallout is discussed in this report. RESULTS Dose rates on D+ 1 Gamma dose rates at Rongelap Atoll on D + 1 (time of detonation plus one day) were estimated to be 3.5 r per hour at the inhabited islet of Rongelap in the south and 35 r per hour at uninhabited Lomuilal islet in the northern part of the atoll (2) , Fig. 1. These estimates were based on extra- polations of measurements made two days after initial fallout The subsequent decline of gamma dose rates, based on survey meter readings taken three feet above the ground at Rongelap and Kabelle islets, is compared with the theoretical decay 1 (3) (2) .