Sixteen epileptic patients suffering from focal epilepsy who underwent antiepileptic drug treatment with carbamazepine (CBZ) for the first time were studied. The EEG was recorded at rest with eyes closed, during blocking reaction (BR), fixation (FIX) and mental arithmetic tasks. The computerized EEG study, performed before and after CBZ therapy, utilized spectral analysis. Data underwent statistical evaluation through Anova and correlation analysis. The parameters evaluated were the mean frequency and the mean absolute and relative power. The results have shown that after CBZ treatment there is a decrease in the alpha reactivity during BR and FIX, while a significant increase in beta activity was observed during all tasks. The effect of CBZ therapy on EEG activity during cortical activation patterns are discussed.