OBJECTIVE: To evaluate the protective effects of cranberry fruit, which have known antioxidant effects, on infection-induced oxidative renal damage in a rabbit model of vesico-ureteric reflux (VUR). MATERIALS AND METHODS: In all, 36 New Zealand male rabbits were divided into five groups, with a sham operation in four rabbits serving as the control (group 1). To create unilateral VUR the roof of the left intravesical ureter was incised, and VUR confirmed 2 weeks after surgery. In all, 32 rabbits with VUR were divided into four groups; 2, VUR alone (with sterile urine); 3, a group infected with Escherichia coli; 4, with intravesical E. coli instillation but fed cranberries; and 5, intravesical E. coli instillation plus an intraperitoneal injection with melatonin group. At 3 weeks after surgery the rabbits were killed, the kidneys obtained and examined histopathologically to evaluate inflammation, fibrosis and tubular changes. Oxidative renal damage was evaluated by measuring malondialdehyde in the renal tissue. RESULTS: Grossly, the refluxing kidney was larger than the contralateral normal kidney, and the refluxing ureter was dilated and tortuous. Microscopy of tissues from the kidneys in group 3 showed apparent periglomerular mononuclear cell infiltration, tubular dilatation and atrophy, and interstitial fibrosis. The kidneys from groups 2, 4 and 5 showed mild mononuclear cell infiltration with no interstitial fibrosis. The level of malondialdehyde in the kidneys of group 3 was significantly higher than that in group 2, 4 and 5 (P 0.05); the level in groups 4 and 5 did not differ significantly from that in group 2. CONCLUSIONS: This study shows that cranberries have an anti-inflammatory effect through their antioxidant function and might prevent infection-induced oxidative renal damage. Thus, clinically cranberries might be used as a beneficial adjuvant treatment to prevent damage due to pyelonephritis in children with VUR.