Recent findings show that in animals, i.v. self-administration of D-amphetamine, cocaine and phentermine, which act predominantly upon catecholamine (CA) containing neurons, is potentiated following chronic restricted feeding. The objective in this experiment was to determine whether food deprivation would potentiate self-administration of fenfluramine, an anorectic compound which acts predominantly upon serotonin (5HT) containing neurons. When saline and five doses of fenfluramine were made available for i.v. self-administration to naive free-feeding (FF) rats or food-restricted (FR) rats at 80% free-feeding weight, the rate of fenfluramine-reinforced responding did not differ significantly from saline-reinforced responding at any dose or deprivation state. These data suggest that the potentiation of responding which occurs under conditions of chronic restricted feeding is specific to compounds which act predominantly upon CA containing neurons.