The records of 52 patients with major depression who were treated with bilateral electroconvulsive therapy (ECT) were reviewed. Responders and nonresponders were compared on demographic, clinical, and treatment parameters. ECT nonresponders had a longer duration of current depressive episode as well as a greater initial severity of depression. The groups did not differ in age, sex, polarity, presence of psychosis, pre-ECT pharmacotherapy, and treatment parameters other than total electrical charge administered. Patients with long episode duration and greater severity of illness may represent a subgroup of major depressives relatively refractory to ECT and warranting novel therapeutic approaches.