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 of 1954 and June of 1957 the return of the Utirikese and Rongelapese occurred respectively. Body burden data for dogimetrically significant nuclides was obtained throughout the cesidence interval post return primarily by direct in vivo gamma spectroscopy and by indirect bioassay techniques. The dosimetric models used in this analysis 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 eatimated from sequential body burden data and were comparable for both atolls. Variation in body burden history data for a particular nuclide on a particula: 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 20-40 years of age ingested more activity each day than did adolescents and persons greater than 40 years of age. Maximum deviation from the average value of the daily ac- tivity ing:stion rate for members of an age sub-group was no greater than a fac- 25