The effects of the acute administration of sodium-valproate (400 mg po) on plasma ACTH levels were studied in 4 patients with Cushing's disease, 1 with Nelson's syndrome and in 3 with Addison's disease. No significant reduction of corticotropin concentration was observed, as compared to saline infusion. These data do not favor the hypothesis of an inhibitory role of sodium-valproate on ACTH secretion in such patients.