1. Urine samples were collected from four men before and during test cold exposures in Melbourne, Australia, and Mawson, Antarctica. Changes in the response of body temperature to the test exposures showed that the men had acclimatized to cold at Mawson.2. Excretion rates of 17-hydroxycorticosteroids and 17-ketosteroids were significantly greater at Mawson than in Melbourne, in both the pre-exposure and exposure periods.3. Excretion rates of noradrenaline, adrenaline, sodium, potassium and creatinine did not differ significantly between Mawson and Melbourne, nor did urine flow rates.4. During the cold exposure significant increases occurred, to the same extent at Mawson as in Melbourne, in urine flow rate and in all measured urinary constituents except creatinine.