The association between aflatoxin B1 (AFB1) exposure and oxidative stress was extensively examined in 84 adolescents from an area at high risk for hepatocellular carcinoma in China. Plasma level of aflatoxin B1-albumin adducts (AAAs) was associated with AFB1 excretion in urine (r = 0.394, P < 0.001). Urinary AFB1 was also associated with both the urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG) (r > or = 0.479, P < 0.001) and 8-OHdG and hOGG1 levels in peripheral leukocytes (r > or = 0.308, P < or = 0.005). Similarly, AAA was significantly associated with both the urinary excretion of 8-OHdG (r > or = 0.259, P < or = 0.018) and the 8-OHdG and hOGG1 levels in peripheral leukocytes (r > or = 0.313, P < or = 0.004). In addition, urinary 8-OHdG was correlated with both the level of DNA 8-OHdG (r > or = 0.24, P < or = 0.05) and the expression of hOGG1 in peripheral leukocytes (r > or = 0.429, P < 0.001). Protein carbonyl content (PCC) level was significantly associated with not only the level of DNA 8-OHdG (r > or = 0.366, P < 0.001) and the urinary 8-OHdG (r > or = 0.258, P < or = 0.018) but also the expression of hOGG1 in peripheral leukocytes (r = 0.485, P < 0.001). A significant but weak association was found between high-performance liquid chromatograph-electrochemical detection (HPLC-ECD) and enzyme-linked immunosorbent assay (ELISA) for urinary 8-OHdG (r = 0.334, P = 0.002) and between HPLC-ECD and flow cytometry assays for 8-OHdG in leucocytes (r = 0.395, P < 0.001). Significant associations were observed between AAA and PCC and liver function indices (alanine aminotransferase and aspartate aminotransferase). These findings suggest significant contribution from AFB1 exposure to oxidative stress and subsequent repair among adolescents that may impose substantial risk for hepatocarcinogenesis in adulthood in this region.