The control over seizures or at least reduction in their frequency is thought to be the principal aim in the treatment of patients with epilepsy. Nevertheless, the numerous data exist that at least 25-40% patients with primary diagnosed epilepsy are resistant to antiepileptic drugs. In such cases the mode of “probes and errors” prevails in the treatment strategy, and the choice of any new antiepileptic drug depends mainly on the previous experience of physicians and so-called elaborated standards of antiepileptic drugs use. The signs differentiating the patients in relation to their drug response before the treatment are rather scarce and controversial. Nevertheless, the general opinion exists that symptomatic partial forms of epilepsies, especially of traumatic origin and forms with cognitive deterioration (intelligence deficiency), early age at onset and concomitant psychotic disorders (i.e. depression), and status epilepticus, as a rule, are characterized by unfavorable course and poor response to drug treatment. Most of these mentioned factors concern the so-called localized-related forms of epilepsy.