Summary: We report the occurrence of spontaneous LSD (lysergic acid diethylamide)-like flashbacks after seven nondominant unilateral electroconvulsive therapy (ECT) treatments in a depressed patient with a history of hallucinogen abuse and flashbacks in the distant past. The similarity of the patient's reported experiences following ECT to the characteristic descriptions of LSD flashbacks is discussed. The differential diagnosis of LSD flashbacks in this case, and speculations regarding their origin, are also considered.