We describe the clinical course of a boy who developed progressive adrenal failure, beginning with failure of the zona glomerulosa, as part of polyglandular autoimmune disease. Initially the patient presented with hypoparathyroidism and mucocutaneous candidiasis. ACTH tests at ages 8 and 11 yr resulted in a normal response of both mineralo- and glucocorticoids. The constellation of hyponatremia , hyperkalemia, and growth failure at age 14 yr prompted a reevaluation. A repeat ACTH test, assessing individual contributions of zone fasciculata and glomerulosa, showed normal plasma cortisol, desoxycorticosterone, and corticosterone responses and a normal urinary response of 18-hydroxydeoxycorticosterone and tetrahydrodeoxycorticosterone. Urinary 18-hydroxycorticosterone and urinary as well as plasma aldosterone were undetectable. PRA was markedly elevated. The ACTH response of adrenal androgens, presumably metabolic products of the zona reticularis, was also deficient. Antiadrenal antibodies against all three layers of the adrenal cortex were present. Mineralocorticoid therapy resulted not only in normalization of electrolytes and PRA but also in catch-up growth. Repeat testing of fasciculata function at age 19 yr now shows that the patient's cortisol response to ACTH response in abnormal. The course of this patient suggest that in addition to monitoring the electrolyte status, periodic tests for both mineralo- and glucocorticoid synthesis should be performed in children with polyglandular autoimmune disease because progressive adrenal insufficiency may go unrecognized.