Both ventricular enlargement and reduced P3 amplitudes are consistent findings in schizophrenic patients, suggesting that the two measures reflect a common underlying pathophysiological process in schizophrenia. Investigating 14 stabilized schizophrenic outpatients, a relationship between the size of the lateral ventricles as well as of the third ventricle on CT scans and the auditory event-related P3 amplitude was, however, not found. This negative result suggests that ventricular enlargement and reduced P3 amplitudes in schizophrenics reflect different pathophysiological processes. It is assumed that the P3 amplitude is related rather to abnormalities in the temporal lobe of schizophrenic patients.