In thalassemia patients, iron overload can stimulate lipid peroxidation (LPO), thereby generating miscoding DNA adducts. Adducted DNA was measured in the lymphocytes of β-Thal/Hb E patients and healthy controls and in the organs of thalassemic mice. εdA, εdC and M1dG residues were quantified by 32P-postlabeling-TLC/HPLC. M1dG levels in lymphocyte DNA from patients were 4 times as high as in controls, while the increase in εdA and εdC was not significant. Adducted DNA accumulated in the liver of thalassemic mice having >2.7 mg Fe/g tissue dry weight; DNA adducts and iron were highly correlated. edA was not specifically generated in certain mouse liver cell types as revealed by immunohistochemical staining. We found elevated LPO-induced DNA damage in the liver of thalassemic mouse and in lymphocytes, implicating that massive DNA damage occurs in the liver of thalassemia patients. We conclude that promutagenic LPO-derived DNA lesions are involved in the onset of hepatocellular carcinoma in these patients. © 2009 UICC.