Changes in psychiatric symptoms following electroconvulsive therapy (ECT) were related to alterations in global EEG and cerebral blood flow (CBF) in 21 in-patients suffering from depression They were examined by clinical ratings, EEG, and CBF immediately before and 1 to 3 h after treatments during an ECT series and at follow-up Four symptom clusters from a factor analysis of symptoms in depression, representing different dimensions of emotion, cognition, and psychomotor retardation, were used for clinical description. The changes in the separate symptom clusters showed different patterns and also different correlations with neurophysiological (EEG and CBF) changes during the course of serial ECT Furthermore, acute clinical and neurophysiological effects following single ECT's were found to be different from non-acute changes, building up during the treatment course. Acute relief in symptoms of anxiety, depressed mood, and psychomotor retardation correlated with an acute slowing of the EEG Regarding non-acute effects a reversed relationship was found, i e improvement in symptoms of depressed mood and psychomotor retardation was related to less EEG slowing As opposed to the acute clinical changes, the non-acute changes, found following the first two or three treatments of a series, contained predictive information about the individual clinical outcome of the patients.