Previous experiments have shown that both cocaine and d,l-cathinone can function as positive reinforcers when delivered intravenously to rhesus monkeys. However, the relative reinforcing efficacies of these compounds have not been established. In the present experiment, three rhesus monkeys were allowed to choose between saline and several doses of d,l-cathinone or cocaine as well as between several doses of both drugs in a discrete-trial choice procedure. Sufficient doses (.05 to .2 mg/kg/injection) of either drug maintained self-administration and the higher doses were reliably preferred to saline. Doses of d,l-cathinone that were preferred to saline were then compared to a range of cocaine doses in drug-drug choice. As the dose of d,l-cathinone that was available was increased, an increase in cocaine dose was necessary to maintain cocaine preference. Comparison of drug-drug choice data to dose combinations predicted to be chosen with equal frequency revealed that the reinforcing efficacy of d,l-cathinone was equivalent to that of cocaine.