A female patient of 32 with a primary hyperaldosteronism has been observed; the case demonstrated some clinical and biochemical specialities. Characteristic symptoms were stated: hypertension, hypokalemia, alkalosis, hyperkaluria and hyperaldosteronuria, but there were no serious muscular troubles or nephropathy of potassium depletion. The intensity of mineral disturbances and hyperaldosteronuria was inconstant. Histological examination showed a typical Conn adenoma formed by fasciculata-like cell formations, obviously still growing. Biochemical examination of the tumorous tissue revealed a specific production of aldosterone, a production of cortisol, a great deal of 11-desoxycortisol and androgens and little corticosterone. The preoperative finding of a slightly increased urinary excretion of neutral 17-ketosteroids, dehydroepiandrosterone and androsterone corresponded to the steroid spectrum of the adenoma. Problems resulting from the diagnostic terminology of adrenocortical hyperfunction were discussed.