We investigated the effects of leukotrienes (LTs) C₄ and D₄ on renal function and hemodynamics of dogs. LTC₄ (0.5 μg/min, infused into the renal artery), but not LTD₄ (1 μg/min), caused an increase in renal blood flow, urine flow, urinary excretion of sodium and potassium, and rate of free water reabsorption, with a concomitant rise in systemic blood pressure. Intrarenal infusion of LTC₄ under conditions of constant renal perfusion pressure induced no significant effect on renal blood flow or urine formation. Infusions or LTC₄ and LTD₄ into the renal artery induced no change in the release of prostaglandins, PGE₂, PGF_2α, 6-keto-PGF_1α or thromboxane B₂ into renal venous blood. From these findings, we concluded that the renal effects of LTC₄ were secondary responses to a rise in systemic blood pressure.