Mice were trained on a one-trial inhibitory avoidance task and given immediate post-training intraperitoneal injections of cocaine (0.03-1.00 mg/kg). On a retention test 24 h later, the retention latencies of mice given the 0.10 mg/kg dose were significantly higher than those of the controls. The effect of cocaine on retention was time-dependent: retention latencies were not altered in animals given cocaine 60 min after training. Administration of cocaine (0.1 mg/kg) prior to the retention test did not modify the retention performance of mice that received either saline or cocaine (0.1 mg/kg) immediately post-training. The findings suggest that cocaine affects retention by influencing post-training processes involved in memory storage.