Five experiments which investigated thermal balance in two clothed men in the cold were carried out at Little America V in the winter months of June and August. Environmental temperatures ranged between - 32° and -47° C, and wind velocities ranged between 2 and 17 miles per hour during the experiments. Despite the protective clothing worn and the heat productions of between 3 and 4.8 mets (measured by indirect calorimetry), total heat debt (obtained by measurements of rectal and skin temperatures) ranged between 105 and 126 kilocalories for exposures of 40 to 165 minutes in duration. Finger temperatures ranged between 7° and 18° C at the end of the experiments. The thermal demand of the environment on these seemingly adequately clothed men was high, and it is suggested that they were moderately cold stressed despite high rectal temperatures.