This series of experiments investigated the effect of the benzodiazepine diazepam on memory formation in day-old chicks trained on a single-trial, passive-avoidance task. The findings indicate that diazepam has a dose-specific and time-dependent effect on memory processes. A 0.125-mg/kg dose of diazepam administered immediately after training led to amnesia in these subjects only after 30 min following learning. Pretreatment with bicuculline and flumazenil were effective in ameliorating the memory deficits caused by diazepam, and consolidated memory function in saline-treated controls following strong and weak aversant training. These findings suggest that benzodiazepine effects on memory are mediated by their effects on arousal, possibly by the release of noradrenaline, which is critical to the establishment of long-term memory.