Chronic unilateral ureteral obstruction (UUO) in the neonatal rat causes delayed renal maturation, tubular apoptosis and interstitial inflammation. Vascular endothelial growth factor (VEGF) acts as a survival factor for tubular cells, and reduces renal injury in several models of renal disease. To determine whether exogenous VEGF attenuates renal injury from UUO, rats were subjected within the first 48 h of life to sham-operation, partial UUO, or complete UUO. Saline vehicle or VEGF₁₂₁ (50 mg/kg) was injected twice daily for 7 days, after which kidneys were harvested for histologic study. The density of peritubular capillaries was measured with PECAM-1 immunostaining, proliferating nuclei were detected by PCNA staining, apoptosis by the TUNEL technique, macrophages by ED-1 immunostaining, and collagen by Sirius red staining. Glomerular number and maturation index were also determined in each group. Following chronic complete UUO in the neonatal rat, peritubular capillary density was significantly decreased. Cortical capillary density was further reduced by exogenous VEGF in the partially obstructed kidney. While UUO also decreased glomerular number and delayed glomerular maturation, exogenous VEGF exerted no additional effects. Cellular proliferation and tubular apoptosis increased in proportion to the severity of obstruction, but exogenous VEGF had no additional effects on proliferation, tubular apoptosis, or macrophage infiltration. However, VEGF reduced interstitial apoptosis in the kidney with partial UUO. We conclude that VEGF does not have salutary effects on the renal lesions caused by chronic UUO in the neonatal rat, and may actually worsen obstructive nephropathy by aggravating the interstitial lesions.