Cognitive and clinical changes during hospitalization were examined in 48 elderly patients with major depression treated with electroconvulsive therapy (ECT) and 55 elderly depressed patients not treated with ECT. Cognitive changes with ECT involved orientation, attention and calculation, and recall. The maximal decrement during ECT averaged 3 points on the Mini-Mental State Examination and occurred after two thirds of the treatments were administered. Baseline cognitive values returned by time of discharge. The affective symptoms improved throughout the course of treatment and remained improved while cognition returned to normal. Patients not receiving ECT showed slightly improved cognitive performance during hospitalization and small, gradual, clinical improvement.