The authors review their experience with brain magnetic resonance (MR) imaging in elderly patients with depression referred for electroconvulsive therapy (ECT). A variety of brain changes were identified on the pre-ECT MR scans of these patients, including cortical atrophy, subcortical encephalomalacia, lateral ventricular enlargement, and lesions of the pons. The authors examine the effects of these preexisting brain changes on the therapeutic outcome and side effects from ECT. Pilot data suggest that these brain findings do not change during a course of ECT. The potential relationship of these brain changes to the development of affective disorder in the elderly is discussed and areas for future research are suggested.