One epileptic seizure elicited by Flurothyl cause impairment of learning in water maze. It is not related with neuronal death occurrence. In our pervious experiments was demonstrated that hypoxic preconditioning (3 days prior the seizure) improves the learning. The same effect was observed after the application of melatonin 1 h prior the seizure. We suppose that this effect is probably due to the scavenger effect of melatonin. Therefore we tested time relation of its application. The experiments were performed on young male Wistar rats. Application of melatonin (100 mg/kg) 2,5 min after the seizure improved the last phase of learning since the 4th day. The effect of melatonin application 6 h after the seizure was not apparent. Pretreatment with melatonin 1h prior the hypobaric hypoxia decreases its preconditioning effect. Our results strongly supports the role of free radicals in the learning impairment after the seizure.