The influence of 1-(3-methylaminopropyl)-di-benzo[b,e]-bicyclo-[2,2,2]octadiene hydrochloride (preparation Ciba 34,276-Ba) on the cortical EEG was studied in 50 healthy volunteers of both sexes aged between 20 and 45 years. EEG tracings were recorded before medication, and then on two consecutive days of treatment with 3 x 50 mg daily, i.e. after total doses of 150 and 300 mg. The percentages, frequencies and amplitudes of the α-waves in each of the three tracings were determined and compared. Quotients of the wave percentages, frequencies and amplitudes for the occipital/frontal, occipital/parietal and parietal/frontal brain regions were calculated. The tracings were examined for slower or faster waves and specific seizure activity. The clinical picture was taken into consideration. The results indicate that the preparation exerted an activating effect on the α-waves with a slight tendency towards synchronization and slowing. The differences became more pronounced after further treatment. Clinical signs of tranquillization and occasional psychomotor retardation were observed. Signs of tiredness were seen in some cases after the first dose, but these did not recur with further medication. No arousal effect was evident. It is assumed that the preparation acts via the limbic moderator and stimulates the components responsible for synchronizing the EEG and stabilizing psychic activity. The effect of short-term, controlled administration of the trial substance on the cortical EEG of healthy persons differs in a positive sense from that of other antidepressants. Detailed evidence in support of this finding will be presented in a later communication.