Quantitative EEG analyses in combination with certain statistical procedures may be utilized in order to classify psychotropic drugs and to determine their cerebral bioavailability. Psychometric tests including evaluation of attention, concentration, psychomotor activity, critical flicker frequency, reaction time, Archimedean spiral, mood and affectivity, may add valuable information about a drug's psychotropic and pharmacodynamic properties. As was seen in studies involving a new pyridodiazepine, short-term drug effects in the EEG of normals are predictive of EEG and clinical effects in patients. Pharmaco-EEG profiles of lopirazepam were found similar in normals and alcoholic patients with an anxiety syndrom as far as the type of changes was concerned, although some quantitative differences were observed. As previously described, quantitative EEG changes during treatment were correlated with clinical improvement or deterioration. Moreover, there is some evidence that single dose effects in the EEG of patients may eventually be utilized to predict therapeutic outcome with a certain drug. Finally, relationships between blood level, quantitative EEG and psychometric changes after administration of phentermine and oxazepam are described and discussed.