Exposing a rat's tail to an ambient temperature lower than that sensed by the rest of the body causes an increase in body temperature. Pretreatment with d-amphetamine causes an even greater increase in body temperature. Morover, while control rats perceive any ambient temperature below 20 degrees C as 'cold', amphetamine-treated animals only perceive ambient temperatures below 20 degrees C as 'cold'. This effect of d-amphetamine was found not only when the body temperature of the rats was 20 degrees C, but also when the body was kept at ambient temperatures of 15 degrees--4 degrees C. Because this effect of d-amphetamine, i.e., shifting of the reference point among treated rats, was found in two other situations (behavioral thermoregulation and in studying the anorexic effects of d-amphetamine among rats kept at different ambient temperatures), the best explanation is that in addition to the effects of the drug upon some thermal sensory roles, it also causes a change in the value of the set point of the thermoregulatory system, and drug-treated rats perceive ambient temperatures of 10 degrees C as 'normal'.