Four antiepileptic drugs were investigated in an inhibitory avoidance task in mice. Following IP administration 30 min prior to training, carbamazepine (32 mg/kg), phenytoin (30–60 mg/kg), diazepam (2–8 mg/kg) and clonazepam (0.125–0.5 mg/kg) impaired retention. When administered 30 min prior to the retention test none of the drugs under investigation affected retention. The drugs did not affect latencies in the hot plate test. This indicates that in the case of pretraining drug administration effects on retention cannot attributed to elevated pain thresholds. Carbamazepine and phenytoin impaired avoidance learning at doses above those which prevent electroshock induced tonic hindlimb convulsions. Diazepam and clonazepam were effective at lower than anticonvulsant doses. The results of the study are relevant to the evaluation of CNS side effects of antiepileptic drugs in mice.