Male CF-1 mice were tested 48 h after training in a one-trial step-through inhibitory avoidance task. Immediately post-training i.p. injections of the antiepileptic drug gabapentin (1-aminomethyl cyclohexaneacetic acid) (GBP; 5, 10, 50, and 100 mg/kg) induced a dose-dependent enhancement of retention performance. Gabapentin did not affect response latencies in mice not given the footshock on the training trial, indicating that the actions of GBP on retention were not due to non-specific proactive effects on response latencies. The effects of GBP (10 mg/kg) were time-dependent, and the administration of GBP (10 mg/kg) 30 min before training also enhanced retention performance. However, the administration of GBP (10 mg/kg) 30 min prior to the retention test did not modify retention latencies of mice that had received either saline or GBP (10 mg/kg) immediately after training. Altogether, the results suggest that GBP influences retention by modulating time-dependent processes involved in memory storage, although the mechanism(s) of this action remain to be established.