We assessed the inhibitory effect of DuP 753, an orally active angiotensin II receptor antagonist, on the pressor action of exogenous angiotensin I and II in healthy volunteers. In a single dose study, doses of 2.5, 5, 10, 20, and 40 mg of DuP 753 or placebo were tested serially at one week intervals. In the multiple dose study, the administration of placebo or DuP 735 (5, 10, 20, or 40 mg, per os once daily) for eight consecutive days was evaluated. The blood pressure response to angiotensin I and II was inhibited in a dose-dependent fashion with a blocking effect still present 24 h post drug. DuP 753 also induced a dose-dependent compensatory rise in plasma renin. This new compound was well tolerated by these normal volunteers. Thus, DuP 753 appears to be a well tolerated, orally active, potent and long-lasting antagonist of angiotensin II in humans.