The EEG has been a widely-used screening procedure before ECT. Previous studies have correlated seizures and post-ECT slowing with ECT efficacy. We investigated the utility of pre-ECT EEG in predicting therapeutic response and post-ECT confusion. EEGs were normal in 54 of 100 patients undergoing first courses of ECT for refractory depression. Patterns within the normal range, were present in 26/100 while 2/100 had paroxysmal discharges without clinical evidence of epilepsy. Focal and generalized EEG slowing were each present in 9/100 records. Full recovery occurred after ECT in 66.6 per cent of those with normal pre-ECT records, 61.5 per cent with borderline EEGs, 55.5 per cent of patients with diffuse EEG slowing, and 22.2 of cases with focal slow waves. Of those with EEG slowing 22.2 percent had little or no response to ECT as compared to 19.2 per cent with EEGs within normal limits and 9.3 per cent with normal EEGs. Four of 6 patients with prolonged confusion had normal EEGs, while 1 each had focal and generalized slowing. EEG slowing was related to incomplete ECT response, but not to therapeutic failure or post-ECT confusion. The limited predictive power of pre-ECT EEG may reflect the prevalence of normal or nonspecifically abnormal EEGs in psychiatric patients and the general efficacy of ECT. Other neurophysiologic methods may yield more definitive information about the mechanism and use of ECT.