When the psychiatrist Hans Berger found that brain potentials could be recorded through the intact human skull, he believed that this procedure would provide an objective correlate of psychopathological phenomena which would prove valuable in psychiatric diagnosis. That this did not materialize was the great disappointment of his life.1 Most workers would still agree with Ellingson, who stated in 1955 that the EEG, interpreted by the traditional method of visual inspection, is of no value in the differential diagnosis of mental disorders.2 Clinical electroencephalography has similarly proved valueless in the assessment of change during the course of the psychosis. It is in these two areas that psychiatry is most in need of objective measures, and it is here that a recently developed quantitative method of studying the EEG gives promise of considerable assistance. The continuous and automatic measurement of