Sulfolane toxicity may be partially due to its effects on body temperature. To examine the effects of sulfolane on thermoregulation, the authors measured metabolic rate and body temperature in rats injected intraperitoneally with sulfolane at dosages of 0, 200, 400, and 800 mg/kg. At ambient temperatures (Ta) of 15 and 25 C sulfolane caused a dose related inhibition in metabolic rate and hypothermia 60 minutes post-injection. At a Ta of 35 C sulfolane had no effect on body temperature or metabolic rate. The hypometabolic and hypothermic effect of sulfolane at a Ta of 25 C lasted at least 2.5 hrs. Sulfolane had a similar effect on body temperature at Ta's of 15 and 25 C, hence, the sulfolane-treated rat had some control over body temperature with decreasing Ta.