In thalassemia patients, iron overload can stimulate lipid peroxidation (LPO), thereby generating miscoding DNA adducts. Adducted DNA was measured in the lymphocytes of beta-Thal/Hb E patients and healthy controls and in the organs of thalassemic mice. epsilondA, epsilondC and M(1)dG residues were quantified by (32)P-postlabeling-TLC/HPLC. M(1)dG levels in lymphocyte DNA from patients were 4 times as high as in controls, while the increase in epsilondA and epsilondC 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. epsilondA 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.