Five male Beagle dogs were obtained from a moderate climate and were immediately subjected to 4-weeks indoor exposure to a warm control environment. This was followed by gradual exposure for ten days to outdoor winter temperatures in the Arctic, after which they were subjected to continuous outdoor exposure. Measurements of insulin sensitivity and glucose tolerance were made during the control and cold-exposed condition. They indicated little, if any, effect of cold acclimatization on insulin sensitivity, although some changes in the shape and the position of the blood glucose curve following insulin injection were noted. Cold acclimatization was associated with an increase in the glucose tolerance.