During the 1950s, with the Cold War looming, military planners sought to know more about how to keep fighting forces fit and capable in the harsh Alaskan environment. In 1956 and 1957, the U.S. Air Force’s former Arctic Aeromedical Laboratory conducted a study of the role of the thyroid in human acclimatization to cold. To measure thyroid function under various conditions, the researchers administered a radioactive medical trace, Iodine-131, to Alaska Natives and white military personnel; based on the study results, the researchers determined that the thyroid did not play a significant role in human acclimatization to cold. When this study of thyroid function was revisited at a 1993 conference on the Cold War legacy in the Arctic, serious questions were raised about the appropriateness of the activity-whether it posed risks to the people involved and whether the research had been conducted within the bounds of accepted guidelines for research using human participants. In particular, there was concern over the relatively large proportion of Alaska Natives used as subjects and whether they understood the nature of the study. This book evaluates the research in detail, looking at both the possible health effects of Iodine-131 administration in humans and the ethics of human subjects research. This book presents conclusions and recommendations and is a significant addition to the nation’s current reevaluation of human radiation experiments conducted during the Cold War.