Figure 25 demonstrates the external exposure following the 1958 testing se- ries. Since return to Rongelap followed 3 years after the BRAVO contamination, this series contributed in large part to the external exposure post return. SUMMARY The Castle BRAVO shot of March 1954 caused the contamination of the inhabited atolls Rongelap and Utirik. Evacuation from Rongelap commenced 50 hours after detonation and from Utirik 55 hours after detonation. During June 1954 and June 1957 the return of the Utirikese and Rongel ape se occurred respec- tively. Body burden data for dosimetrically significant nuclides were obtained throughout the residence interval post return primarily by direct in vivo gamma spectroscopy and by indirect radiochemical analysis of urine and blood. The dosimetric models used in this andlysis were representative of a declining continuous uptake regime. Dietary decline of radioactivity included radioactive decay of the source and a conglomerate of other factors which might have included increased use of imported foods and weathering of the source. Di-~ etary loss rate constants were estimated from sequential body burden data and were comparable for both atolls. Variation in body burden history data for a particular nuclide on a particular atoll was observed in whole body counting data and urine bioassay results. This was attributed principally to the statistical variation encountered when small groups are sampled from a heterogeneous group of body burdens in people, and in the case of urine bioassay additional variation was introduced during the laboratory analysis of samples. Daily activity ingestion rates were determined for all measured radionuclides. In general, infants, children, and adults between 20 and 40 50