Variation between atolls in risk of radiation-~induced thyroid cancer and the difference when compared to. other irradiated groups had become an important scientific and health-related question with the considerable political overtones. Early in 1977, Bond, Borg, Conard, Cronkite, Greenhouse, Naidu, and Meinhold, all members of Brookhaven National Laboratory (BNL), and Sondhaus, University of California, College of Medicine, initiated a reexamination of the technical issues. In 1978, formal program objectives and funding were supplied to BNL by the Department of Energy's Division of Biological and Environmental Research. In June 1978, the Meteorology Division at Lawrence Livermore National Laboratory was subcontracted to provide 4 computer simulation of the dispersion, transport, and deposition of fallout from the 1954 atmospheric nuclear test, BRAVO. A subcontract to provide neutron activation analysis of archival soil samples was given to the Radiological Sciences Department, Battelle-Pacific Northwest Laboratory. Soil samples were provided by Seymour, the director of the University of Washington's Laboratory of Radiation Ecology. Thyroid absorbed dose tabulated here was estimated from results on 131; activity excreted in urine and the specific nuclide composition of BRAVO fallout. Surface and airborne activity, fallout granule size, and exposure rate at times after the detonation were developed for 142 nuclides at Rongelap and Utirik on the basis of the reported nuclide composition on day 26 post- detonation. Over 70 documents were reviewed for information regarding exposure-rate readings, film-badge readings, fallout composition, dose and dose rate, body burdens, urine analyses, gastrointestinal tract contents, bone marrow and thyroid dose estimates, and activity measurements in soil, water, marine life, and land animals. Results from the meteorology study and archival soil study were also reexamined and compared to fallout composition results. A tabulation of the estimates of thyroid absorbed dose, age at exposure and specific nuclides was done for each location. For an adult male, the thyroid absorbed dose from iodine and tellurium nuclides was 7.7 times the absorbed dose due to I at Rongelap, 10 times at Sifo Island and 4.7 times at Utirik Island. James pypumed the total thyroid absorbed dose was 2.6 times the absorbed dose due to I (Ja64). The factor 2.6 would be appropriate for slightly older fallout than that experienced at Rongelap, Utirik or Sifo Islands. Thryoid absorbed dose was based on ingestion intake. Inhalation intake and absorption through skin could not be reconciled with measurements of I in urine or with external exposure rate measurements. Observations of the range of 137¢., body burdens during protracted exposure (Mi79) and the range associated with the contents of the stomach in cases of sudden death (Ev66) were used to estimate maximum thyroid absorbed dose. Thg average internal thyroid dose at Rongelap Island was based on the average I activity collected in urine. The contribution to thyroid dose from external sources was estimated from the air exposure created by 142 nuclides which were estimated from results of BRAVO fallout composition. external dose was similar to original estimates by Sondhaus for persons exposed at Rongelap and Utirik Islands. The The original external dose estimates at these islands, 1.75 gray and 0.14 gray (175 rad and 14 rad) respectively, were derived from survey instrument readings taken after evacuation and film