The urinary concentration of 8-hydroxydeoxyguanine (8-OHdG), which is a biomarker of oxidative DNA damage, was measured in 248 healthy Japanese, and its correlations with life style, urinary metal elements, serum antioxidants, and other plasma or serum factors were investigated. The mean urinary concentration of 8-OHdG was 15.2+/-5.71 ng/mg creatinine. Mean urinary 8-OHdG was not significantly different in terms of age (<45, >or=45), gender, smoking (no, <20, >or=20), and alcohol consumption (no, occasionally, sometimes and usually). Moreover, multiple regression analysis showed a significant association between urinary 8-OHdG and urinary arsenic (As) or chromium (Cr), and a tendency for association between the former and aluminum (Al) and nickel (Ni). Age, gender and plasma or serum factors including antioxidants, lipid peroxide, HbA1c, BUN, and iron did not show such an association. The present study suggests that natural exposure to toxic metal elements such as As, Cr, and Ni may influence oxidative DNA damage in healthy people under usual environmental management. Therefore, the measurement of urinary metals such as As, Ni and Cr is prerequisite for the study of the relationship between urinary 8-OHdG and other variable factors.