Responding was established in squirrel monkeys under a modified progressive ratio schedule of IV d-amphetamine or cocaine self-administration. Subsituation of saline for the drug solutions resulted in extinction of the self-administration behavior. IV injections of certain doses of d-amphetamine or cocaine, immediately prior to test sessions in which response-contingent saline infusions were delivered, reinstated the rate and pattern of responding observed during sessions in which drug was self-administered. Presession IV injections of several doses of pentobarbital or chlorpromazine failed to consistently reinstate responding. These results were interpreted in terms of the discriminative control of drug self-administration behavior by the current drug state of the subject.