Frequent tonic-clonic seizures could probably lead to psychic disorders. In various studies a decrease in at least single functions of mental capability was found depending on the frequency of the seizures and/or the duration and/or the age of onset of the disease. The development of neuropsychological deficits depends on the type of seizures. Particularly BNS-seizures and the Lennox-Gastaut-syndrome have generally a poor prognosis concerning the intellectual development. Not only clinically manifest seizures but also subclinical discharges could disturb the psychic condition of epileptic patients. Epileptic seizures are probably a reason for neuronal damage in the hippocampus area. Psychogenic reactions and undesired effects of antiepileptic drugs have to be considered aside from functional disturbances due to epileptic seizures.