The authors review the results of electroconvulsive therpay (ECT) in 135 cases of depression occurring in conjunction with organic dementia, subcortical leukoencephalopathy without dementia, and depressive dementia (22 cases). Overall, 86% had a positive therapeutic response to ECT, whereas 21% experienced significant cognitive or memory side effects, virtually all of which were transient and reversible. Forty-nine percent of the patients with organic or depressive dementias experienced improvement in cognitive or memory function consequent to ECT.