Sulfolane is a solvent which produces hypothermia and decreased oxygen consumption following acute exposure. In the present experiment, the author investigated effects of sulfolane on a behavioral measure of toxicity at ambient temperatures which would either prevent or facilitate the development of hypothermia. Adult, male Long Evans rats (N=10/dose) received a single i.p. injection of saline, 200, 400 or 800 mg/kg sulfolane. Motor activity in figure-eight mazes was assessed 1 hr after dosing in testing rooms maintained at either 20.8 C or at 32.3 C. At the warm ambient temperature, sulfolane produced hypoactivity but not hypothermia. At the cooler temperature, sulfolane-induced hypoactivity was more pronounced, and rats were hypothermic. Therefore, a behavioral change could be detected at sublethal dosages of sulfolane in the absence of hypothermia.