SummaryAmmonium chloride does not inhibit the hypertensive effect of desoxycorticosterone acetate in the rat. When both received the steroid, no difference can be detected between the blood pressure of rats given excess sodium chloride or an equivalent amount of ammonium chloride. The protection against cardiovascular lesions by NH4Cl in DCA treated animals must therefore be ascribed to a lack of response of the vascular territories to hypertension.