The remarkable side effect of cisplatin, a cytotoxic agent in cancer treatment, is acute renal failure which limited its clinical uses. An increase in free radicals has been shown to play an important role in this renal pathogenesis. Our previous studies have shown a significant increase in renal melondialdehyde level on day 3 along with a marked reduction in renal blood flow, glomerular filtration rate and urinary Na+ and K+ excretion on day 3 and day 7 after cisplatin (7.5 mg/kg i.p.) injection in rats. The number of survived animals and the degree of renal damage assessed by clearance technique have been improved with quercetin, a strong antioxidant, co-treatment. In this study, we used histopathological scoring analysis of glomerular and tubular lesions on day 3, 7 and 14 after 7.5 mg/kg cisplatin i.p. injection in rat to strengthen our prior data. The protective effects of oral administration of quercetin, 50 mg/kg, twice 24 hr and 10 min, before cisplatin injection were thoroughly determined. Experiments were performed in male Wistar rats, 200-300 g. The number of rats in each sub-groups were between 5-11. All experimental rats were maintained and handled according to the approval of the Prince of Songkla University Animal Ethics Committee. On the day of experiment, the animals were anesthetized with 60 mg/kg pentobarbitone sodium, i.p., then, the kidneys were retrograde perfused and isolated. Each kidney was longitudinal cut into two pieces and fixed in 10% buffer neutral formalin for 24 hrs before further process. The embedded renal tissues were sectioned at 6 μm thick ribbon and stained with hematoxilin and eosin. Glomerular injury was defined according to the percentage of glomerular atrophy in the renal cortex whereas renal tubular injury grading was defined by the percentage of nuclear swelling, pyknosis and karyorrhexis and tubular dilatation in renal cortical and outer strip of outer medullary area. Intraluminal hyaline cast formation was also randomized graded in both cortex and medulla. Both glomerular and tubular lesions were classified into five grades according to the degree of damage incremently. It is found that the oral co-administration of quercetin with cisplatin injection blunted the progressive lesions of glomerular atrophy, tubular dilatation and intraluminal hyaline cast formation observed on day 7 and 14 but blunted the tubular nuclear damage observed on day 3, 7 and 14. These effects were indicated by the significant reduction in the number of rat with higher lesion grades. It is noticed that one of the mechanisms responsible for the renal protective effect of quercetin in cisplatin- induced acute renal failure rats is via glomerular and tubular structural remodeling.