EEG recordings from 5 different brain areas of freely moving rats were performed under controlled vigilance stage conditions. Effects of antidepressant and neuroleptic drugs were assessed following their intraperitoneal injection. Quantification of the drug effects was achieved by analysis of variance following on-line fast-Fourier transformation of the EEG signal. This resulted in so-called drug profiles. From the individual antidepressant and neuroleptic drug profiles, an antidepressant and neuroleptic drug class profile was calculated. Using the absolute power for the calculation of the antidepressant and neuroleptic drug class profiles gave a better discrimination between the two drug class profiles than using the relative power. The antidepressant and neuroleptic drug class profiles derived from the n. amygdala and hippocampus did not show significant differences. The antidepressant and neuroleptic drug class profiles showed significant differences (p < 0.05) in rather small frequency bands from the n. caudatus (16–14 Hz), n. accumbens septum (19–24 and 27–31 Hz) and cortex (10