Hepatocellular carcinoma (HCC) is one of the most common fatal cancers worldwide. Hepatitis B virus and hepatitis C virus infections, exposure to aflatoxin, and excessive intake of alcohol have been identified as major risk factors. However, the molecular mechanisms underlying their development are still poorly understood. Recently, β-catenin, one of the key components of the Wnt signaling pathway, has been found to be mutated in about 20% of HCCs, suggesting a role of the Wnt pathway in their development. In this study, we examined β-catenin and APC mutations in 22 HCCs associated with HCV infection, using single-strand conformation polymorphism (SSCP) followed by direct DNA sequencing. β-Catenin mutations were found in nine (41%) cases, but no APC mutations were found. β-Catenin immunohistochemistry revealed nuclear accumulation of β-catenin protein in all nine tumors with a β-catenin mutation and two additional tumors without a mutation. These results suggest that activation of the Wnt signaling pathway by β-catenin mutation contributes significantly to the hepatocellular carcinogenesis associated with HCV infection.