The authors studied patterns of corticotropin (ACTH) secretion following single and multiple electrically induced convulsions in the course of treating seven psychiatric patients. All seven patients improved clinically after administration of ECT along with other rehabilitative and therapeutic measures. The pattern of ACTH release during ECT was found to be similar to the pattern during other known physiological stresses. Serial seizures produced sustained high ACTH levels that fell to basal levels at the same rate as the fall after a single convulsion. One patient who had been receiving supraphysiological doses of steroids showed no rise in ACTH during five serial seizures. The authors discuss the clinical and heuristic implications of these results.