PREFACE The purpose of this report is to document the detail and data used to estimate thyroid absorbed dose to persons exposed to high levels of early fallout. The scope of the work was defined by historical records containing environmental measurement results and testing data for'detonations in the Marshall Islands, particularly reports concerning the Castle BRAVO detonation. The records were serutinized and data were subjected to a variety of analyses. The results of this work show agreement between measured radiological results and the required radiobiological projections. The new estimated thyroid absorbed dose and the medical factors relating to health effects in the Marshall Islands may be used to estimate potential health effects in other populations exposed under similar conditions. . - 111 moe pom may Dap ke wu we U NL ah