We evaluated the effect of initial oxcarbazepine (OXC) monotherapy on memory, attention and simple psychomotor speed in 14 patients; 15 patients with initial phenytoin (PHT) monotherapy served as reference patients. Neuropsychological assessments were performed before starting the treatment and after 6 and 12 months follow-up with steady-state drug treatment. Differential cognitive effects of OXC and PHT were not apparent in our study. As the efficacy of present antiepileptic drugs in adult epilepsy is analogous, the choice of drug is determined by the comparative side effects of the drugs. In the present study the number of successfully treated patients was similar in both OXC and PHT groups. As far as cognitive side effects are concerned our results revealed no evidence favoring either antiepileptic over the other.