A paradigm involving feeding to satiety over the course of repeated trials in the runway was used to examine the effects of d-amphetamine (1.0, 1.5 mg/kg) and d-fenfluramine (2.0, 3.0 mg/kg). 1.0 mg/kg d-amphetamine was found to have no significant effect on running performance or feeding in the runway. 1.5 mg/kg d-amphetamine significantly reduced the total food intake during the test but had little impact during the first three trials. In contrast, d-fenfluramine, even at the lower dose and during the initial trials, significantly reduced running performance and feeding to levels normally associated with satiation in the non-drugged animals. The results are discussed in relation to the contrasting modes of action of amphetamine and fenfluramine on food intake.