Accumulation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in DNA, which may result from the continuous reactive oxygen species (ROS) generation associated with chronic inflammation, has been reported in various human preneoplastic lesions and in cancerous tissues. However, no direct causative relationship between the 8-OHdG formation and carcinogenesis has been thus far demonstrated in humans. Directly proving the causality requires showing that depletion of 8-OHdG levels in tissue by interfering with ROS generation results in a reduction in cancer. Chronic hepatitis C virus (HCV) infection is associated with a high risk of hepatocellular carcinoma (HCC). Several studies on patients with chronic HCV have shown that hepatic iron overload is attributable to liver injury and that iron depletion improved serum aminotransferase levels. Excess iron is known to generate ROS within cells, which causes mutagenic lesions, such as 8-OHdG. In this study, therefore, we have evaluated whether therapeutic iron reduction (phlebotomy and low iron diet) with a long-term follow-up (6 years) would decrease the hepatic 8-OHdG levels and the risk of HCC development in patients with chronic HCV. Patients (34) enrolled were those who had undergone standard IFN therapy but had no sustained response. Quantitative immunohistochemistry using the KS-400 image analyzing system and electrochemical detection was used for 8-OHdG detection. With this treatment, elevated hepatic 8-OHdG levels in patients with chronic hepatitis C (8.3 ± 4.6/10⁵ dG) significantly decreased to almost normal levels (2.2 ± 0.9/10⁵ dG; P < 0.001) with concomitant improvement of hepatitis severity, including fibrosis, whereas HCV titers were unaffected. None of these patients developed HCC. Thus, long-term iron reduction therapy in patients with chronic hepatitis C may potentially lower the risk of progression to HCC.