We have previously shown that bladder urothelium of people living in the cesium-137 ((137)Cs)-contaminated areas of Ukraine demonstrates accumulation of stable p53 and p53 mutational inactivation, preferentially through G:C to A:T transition mutations at CpG dinucleotides, with a codon 245 hot spot. In the present study, we analyzed immuno-histochemically the relationship between oxidative stress markers and over-expression of p53 and H-ras in urinary bladder urothelium from 42 men with benign prostatic hyperplasia. Bladder mapping biopsies were obtained from 15 patients from a highly radiocontaminated area (group I), 14 patients from the less contaminated city of Kiev (group II) and 13 patients as a control group from "clean" (without radiocontamination) areas of Ukraine (group III). Irradiation cystitis with multiple foci of severe dysplasia and carcinoma in situ were observed in 15 of 15 (100%, group I) and 9 of 14 (64%, group II) cases, with 4 small transitional-cell carcinomas incidentally detected in groups I and II. Markedly elevated levels of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2) and 8-hydroxy-2;-deoxyguanosine (8-OHdG) were noted in these bladder urothelial lesions from groups I and II, accompanied by strong over-expression of p53 and less H-ras expression. These findings support the hypothesis that iNOS, COX-2 and 8-OHdG in bladder urothelium are induced by long-term exposure to low-dose radiation with a close relationship to p53 over-expression that could predispose to bladder carcinogenesis.