This study examined the effects of renal arterial infusion of a selective cytochrome P450 epoxygenase inhibitor, N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanoic acid (MS-PPOH; 2 mg/kg plus 1.5 mg kg^-1h^-1), on renal hemodynamic responses to infusions of [Phe²,Ile³,Orn⁸]-vasopressin and angiotensin II into the renal artery of anesthetized rabbits. MS-PPOH did not affect basal renal blood flow (RBF), or cortical or medullary blood flow measured by laser Doppler flowmetry (CLDF/MLDF). In vehicle-treated rabbits, [Phe²,Ile³,Orn⁸]-vasopressin (30 ng kg^-1min^-1) reduced MLDF by 62±7% but CLDF and RBF were unaltered. In MS-PPOH treated rabbits, RBF and CLDF fell by 51±8% and 59±13% respectively when [Phe²,Ile³,Orn⁸]-vasopressin was infused. MS-PPOH had no significant effects on the MLDF response to [Phe²,Ile³,Orn⁸]-vasopressin (43±9% reduction). Angiotensin II (20 ng kg^-1min^-1) reduced RBF by 45±10% and CLDF by 41±14%, but MLDF was not significantly altered. MS-PPOH did not affect blood flow responses to angiotensin II. Formation of epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DiHETEs) was 49% lower in homogenates prepared from the renal cortex of MS-PPOH-treated rabbits than from vehicle-treated rabbits. MS-PPOH had no effect on the renal formation of 20-hydroxyeicosatetraenoic acid (20-HETE). Incubation of renal cortical homogenates from untreated-rabbits with [Phe²,Ile³,Orn⁸]-vasopressin (0.2-20 ng/ml) did not affect formation of EETs, DiHETEs or 20-HETE. These results do not support a role for de novo EET synthesis in modulating renal hemodynamic responses to angiotensin II. However, EETs appear to selectively oppose V₁-receptor-mediated vasoconstriction in the renal cortex, but not in the medullary circulation, and contribute to the relative insensitivity of medullary blood flow to V₁-receptor activation.