Electroencephalograms were recorded from the parietal and frontal cortex of freely moving rats held in constant vigilance by placing them in a slowly turning drum. The effects of 5 clinically effective anxiolytics, buspirone, meprobamate, phenobarbital, chlordiazepoxide and diazepam, were studied after intraperitoneal injection of different doses. After on-line fast Fourier transformation of the EEG signal, the drug effects were quantified by an Analysis of Variance. This resulted in a t profile for each drug dosage. Averaging the t profiles of all dosages of a drug results in a ‘drug profile’. Averaging the drug profiles of the 5 anxiolytic drugs tested results in an ‘anxiolytic profile’. This profile is characterized by a power decrease from 8 to 11 Hz and above 70 Hz and a power increase from 20 to 60 Hz. The anxiolytic profile is compared with the formerly defined antidepressant and neuroleptic profiles and can be clearly distinguished from the lat