In the neonate, chronic unilateral ureteral obstruction (UUO) reduces renal blood flow (RBF) of the ipsilateral kidney and increases RBF of the opposite kidney. To determine whether renal nerves mediate or modulate these responses, complete left UUO in the neonatal rat was used as a model of severe obstructive uropathy, and was compared with sham-operated controls. At 24-28 days of age, animals underwent left or right mechanical renal denervation or left sham renal denervation. One week after denervation, animals were anesthetized and blood pressure and heart rate were measured. Cardiac output and RBF were determined by the radioactive microsphere technique. UUO increased blood pressure and heart rate, and decreased RBF in the obstructed kidney, regardless of denervation. While left UUO increased RBF to the intact opposite kidney in rats with left renal denervation, this was attenuated by right renal denervation. Thus, in the neonatal rat, UUO modulates systemic renal hemodynamics, possibly through activation of the renin-angiotensin system. While renal nerves do not mediate the vasoconstriction of the obstructed kidney, renal nerves modulate vascular tone of the kidney contralateral to UUO.