ABSTRACT In 5 normal men intravenous infusion of 600 ng/kg/min of des-asp1-,ileu8-angiotensin II (AIIIA) inhibited a rise in blood pressure as well as increase in plasma aldosterone caused by an intravenous infusion of 20 or 100 ng/kg/min of des-asp1-angiotensin II (angiotensin III, AIII). This result and our previous study on simultaneous infusions of 600 ng/kg/min of AIIIA and 20 ng/kg/min of angiotensin II (All) in the same 5 normal men demonstrate that this dose of AIIIA antagonizes AIII and All on the adrenal cortex as well as peripheral arterioles and that AIIIA has the same degree of inhibitory effect on the aldosterone-stimulating action of AIII and on that of All in man.