Under the extreme change of the environment, animals react physiologically to adapt to the stress and secrete catecholamines. Cold exposure is a kind of the environmental stress. Author tried to determine the amount of catecholamines in rat urine as a parameter of physiological response to cold stress. Urinary catecholamine was measured by using HPLC with fluorescence detector, cation exchange column prepacked with Bio·Rex 70 and ammonium pentaborate as catecholamine eluent. The amount of dopaminc in normal state rat urine was 42.0 ng, but under the low temperature of $5^{circ}C$, the dopamine amount was increased to 221.25 ng/5 ml. Above findings are suggesting that catecholamine secretion, especially dopamine, increases in the stressful condition such as cold exposure.