Changes of field potentials electrically evoked from the mesencephalon were studied in two dopaminergic target areas. The modulation of the responses in prefrontal cortex and striatum induced by intravenous injection of various compounds influencing central dopaminergic transmission is followed. In general, drugs with a down-regulating effect on dopaminergic impulse activity produced a significant diminution of the response, whereas compounds enhancing dopaminergic impulse flow produced an increase of the signal amplitude. The results are discussed in terms of the usefulness of the evoked potential as a screening procedure for monitoring dopaminergic impulse flow during the evaluation of new drugs against schizophrenia.