SECTION 1 INTRODUCTION AND SUMMARY During the period 1-2 March 1954, twenty-eight Army and Air Force personnel stationed at Rongerik Atoll in the Marshall Islands were exposed to radioactive fallout from Shot Bravo of Operation CASTLE. The purpose of this report is to determine the whole body gamma radiation dose received by these personnel prior to their evacuation from the atoll, plus their organ dose commitments from internal emitters. The gamma radiation dose is reconstructed as follows. The radiological environment resulting from Shot Bravo fallout is determined from time-of-arrival data on Rongerik, modeled deposition, measured decay rates, and a later reading on Rongerik. Personnel activity scenarios are considered in conjunction with radiation shielding factors to arrive at film badge doses on an individual basis. Although film badge readings are available, they relate inadequately to personnel dose. Readings that reflect well-specified exposures indicate good agreement with corresponding calculated doses. A small, but systematic, difference indicates an adjustment to the calculated personnel doses, which are in the vicinity of 40 rem. Organ-specific 50-year dose commitments resulting from the large-particle inhalation and ingestion of Bravo fallout radionuclides are calculated. Intake of iodine-131 is determined from the body metabolism of iodine that led to a measured activity of 1-131 in a pooled urine sample taken 17 days after Bravo. The radionuclide inventory for the time of intake is normalized to the level of I-131 activity, thereby indicating the full intake of radioactivity. Large-particle dose conversion factors for each radionuclide are developed for calculation of internal dose commitments to each organ. The calculated thyroid dose is 190 rem, and intestinal dose is as great as 76 rem. Other organ doses do not add significantly to the external gamma dose.