The effects of hypnosis on thermoregulatory responses were studied in nonacclimatized acutely cold-exposed men. Forty exposures (4.5 @#X2013;5.0 C) were conducted in an environmental chamber under both hypnosis and nonhypnosis conditions. Five subjects, wearing 1 clo insulation, were cold exposed for 1 hr, four times for each condition, and each subject served as his own control. Variables monitored included mean skin and rectal temperatures, heart and shivering rates, basal skin resistance, and vigilance task performance. In hypnosis, shivering was suppressed, heart rate lowered, and vigilance task performance improved. Basal skin resistance differed in terms of pattern and level, being generally higher under hypnotic conditions. Rectal temperatures were lower despite maintaining skin temperature at the same level as during nonhypnosis conditions. These findings indicate that with the thermal stress imposed and levels of trance achieved, there is a general amelioration of the psychophysiological effects of the stress. The mechanism responsible for this form of “adaptation” remains speculative but is consistent with generalized suppression of sympathetic activity.