Electroconvulsive therapy (ECT) is an established effective treatment modality for patients with severe depression. Recent studies have focused on developing predictors of response. In this prospective study, using percent decrease in Hamilton Depression Scale (21 items) as the outcome measure, we blindly evaluated 33 inpatients with major depression to determine whether postictal suppression, the electrical silence following induced seizure, would predict treatment response to ECT. A significant relationship was observed between degree of postictal suppression and likelihood of clinical improvement. Postictal suppression should be explored in more controlled studies as a predictor of ECT response.