Bradykinin (0.05, 0.1 and 0.2μg/kg/min) and eledoisin (0.5, 1.0, 5.0 and 10.0ng/kg/min) were infused directly into the left renal artery of anesthetized dogs to demonstrate the effects of these peptides on renal function. Urinary volume, endogenous creatinine clearance (GFR), PAH clearance (RPF) and excretion of electrolytes were increased by infusion of these two peptides, but no constant change was observed in UK/UNa ratio. These data demonstrate that the increase in urinary output and electrolyte excretion is caused by the augmentation of tubular load of solutes which resulted from the increase of RPF and GFR. Tachyphylaxis was observed in dogs which received repeated infusions of bradykinin but this phenomenon was less distinct in the case of eledoisin.