We investigated the effects of leukotrienes (LTs) C4 and D4 on renal function and hemodynamics of dogs. LTC4 (0.5 microgram/min, infused into the renal artery), but not LTD4 (1 microgram/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, PGF2 alpha, 6-keto-PGF1 alpha 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.