The hypothesis that neuroleptic drugs interfere with operant behaviors by attenuating the rewarding properties of positive reinforcers, was examined in rats trained to lever-press for external heat in a cold environment. Unlike traditional reinforcers, such as food and water, reducing the reward magnitude of heat (by reducing the intensity or duration of the stimulus) results in compensatory increases in operant responding. Neuroleptic pretreatment (0.1, 0.2, 0,4 mg/kg of alpha-flupenthixol) produced only dose-dependent decreases in responding thereby interfering with the animals' ability to behaviorally maintain their internal core temperature. In a temperature-gradient test paradigm (requiring less physical effort on the part of the subjects) alpha-flupenthixol did not alter the animals' preferred environmental temperature, nor did it disrupt behavioral thermoregulatory ability. These data suggest that at least part of the behavioral deficit observed during neuroleptic treatment is due to a disruption in the performance capabilities of the subjects.