The DNA base-modified product 8-hydroxy-2'-deoxyguanosine (8-OHdG) is one of the most commonly used markers for the evaluation of oxidative DNA damage. A monoclonal antibody specific for 8-OHdG (N45.1) was characterized and applied in quantitative immunohistochemistry. N45.1 recognized both the modified base and deoxyribose structure of 8-OHdG and required a concentration two orders higher of 8-hydroxyguanosine as a competitor in the ELISA. In addition, N45.1 did not cross-react with the original four deoxyribonucleosides, other DNA base-modified products such as 8-hydroxy-2'-deoxyadenosine and O6-methyl-2'-deoxyguanosine, or urine components such as uric acid, creatine, and creatinine. A ferric nitrilotriacetate-induced rat renal carcinogenesis model was used for the evaluation of quantitative immunohistochemistry. The 8-OHdG index of quantitative immunohistochemistry, as analyzed by NIH image freeware, correlated reasonably well with the 8-OHdG amount determined by high-performance liquid chromatography with an electrochemical detector-except for a difference in peak time, which could be attributed to the selection of target location. The present method has advantages over the high-performance liquid chromatography/electrochemical detector, gas chromatography/mass spectrometry, and 32P-postlabeling methods in that it allows localization of 8-OHdG to be specified without the risk of artifactual production of 8-OHdG during the DNA extraction and hydrolytic processes.