In order to block the effects induced by the interactions between angiotensin II (AII) and both AT1 and AT2 receptors, we have pursued the discovery of orally active non-peptide AII antagonists that exhibit potent and equal affinity for human AT1 and AT2 receptor subtypes. A series of previously prepared nanomolar (IC50) trisubstituted 1,2,4-triazolinone biphenyl-sulfonamide dual-acting AII antagonists has been modified at five different positions in order to increase AT2 binding affinity, maintain AT1 activity, and reduce the human adrenal AT2/AT1 potency ratio (IC50 ratio) from > or = 10. The targeted human adrenal potency ratio of < or = 1 was achieved with a number of compounds possessing an ethyl group at C5 of the triazolinone and a 3-fluoro substituent at the N4-biarylmethyl moiety. The most favored of these was compound 44 which exhibited subnanomolar potency at both the AT1 (rabbit aorta) and AT2 (rat midbrain) receptors, with a slight preference for the latter, and had a human adrenal AT2/AT1 IC50 ratio of 1. This tert-butyl sulfonylcarbamate with an N2-[2-bromo-5-(valerylamino)phenyl] substituent had excellent iv activity at 1 mg/kg (100% peak inhibition, > or = 4 h duration of action) and is orally active at 3 mg/kg with > 6 h duration of action in a conscious rat model. The present study shows that the NH of the amide on the N2-aryl moiety is not required for subnanomolar binding affinity to either receptor subtype, although a keto functionality at this position is essential for acceptable AT2 binding. Receptor-ligand binding interactions derived from the structure-activity relationships are discussed with respect to both receptor subtypes.