A prolonged (interictal) delirium was induced by electroconvulsive therapy (ECT) in 6/36 (17%) elderly depressed patients. Brain magnetic resonance imaging or brain computerized axial tomography revealed structural changes in the basal ganglia and white matter in all six patients who developed delirium. These findings are consistent with our previous work and with several lines of data that have implicated the basal ganglia and subcortical white matter in the development of delirium from other causes. These result suggest that lesions in these areas may predispose one to developing an interictal delirium during a course of ECT.