Since 1965, the distribution of 55 ne in the biosphere has been studied both in the United States and in the Scandinavian ‘countries. Initially, ore concentrations were determined in “Alaskan Eskimos, residents of Richland, Washington, and in| representative foodstuffs of both (1). Subsequently, 256 concentrations in environmental samples and in residents of Finland (2) and Sweden @) were reported which generally confirmed the findings of the earlier study. “that Additional research shows (i) marine organisms and people whose diet is largely sea- - . food contain the highest concentrations of 556 (4); (13) residents of the northern hemisphere have higher 5556 body burdens than those of the southern hemisphere (5); and (iii) the Fe levels in people reached peak concentrations in 1966 and . continue to decrease (6,7). We determined the 5556 body burdens of natives at Rongelap Atoll in the Marshall Islands. seafoods Not only is their diet high in (8), but the atoll received high-level fallout following the detonation of a thermonuclear device at Bikini Atoll in 1954 (9). We considered it probable that retention of >? Be at the atoll from that event, coupled with world-wide fallout from largescale nuclear device testing in 1961-62 could lead to unusual body burdens of this radionuclide in the Rongelapese. the method of separation of > Fe was identical to that previously described in this journal (1). The counting technique