Mice injected intraperitoneally with sulfolane (tetrahydrothiophene-1, 1-dioxide) undergo a decrease in metabolic rate and body temperature. If given the opportunity, mice treated with sulfolane preferentially seek a cool ambient temperature. At a warm ambient temperature (35 C) neither metabolic rate nor body temperature are decreased by sulfolane. When given the LD50 dose of sulfolane, the percent mortality varies directly with ambient temperature. For example, at 35 C mortality is 75% whereas at 25 C mortality is only 8%. By undergoing an autonomically and behaviorally-mediated decrease in body temperature (i.e., regulated hypothermia), sulfolane-treated mice appear to enhance their chance of survival.