Chlorpromazine (CPZ) and haloperidol (H) have been suggested as possible antagonists of the reinforcing effects of psychomotor stimulant drugs. To test this hypothesis in animals, four rhesus monkeys were trained in a preference procedure to choose between intravenous injections of cocaine or food presentation. Frequency of cocaine choice increased as unit dose of cocaine was increased. Continuous infusions of low or intermediate doses of CPZ or H either did not affect or increased the frequency of cocaine choice. Higher doses of CPZ or H completely suppressed responding for both reinforcers. Although ther appears to be a mutual antagonism of some of the effects of cocaine and these antipsychotic compounds, the results of the present experiment fail to support the hypothesis that the reinforcing effects of cocaine can be antagonized with CPZ or H.