Two patients with low renin hypertension showing an increased urinary excretion with 17-KS, with normal level of plasma deoxycorticosterone and no signs of virilization were reported. Dexamethasone induced reduction in blood pressure and elevation of serum K, in spite of acceleration of the reninangiotensin-aldosterone system. Thus, it has been inferred that the hypertension was not associated with adrenogenital syndrome but was due to excessive production of an unknown mineralocorticoid.