Hepatitis C virus (HCV) is a major causative agent in liver disease. In order to investigate if Korean type HCV core protein and its related mutants, S99Q and S1161, are cytopathic to liver, three types of transgenic mice were established. The expression of transgenes was confirmed by HCV specific RT-PCR and Western immunoblotting. The livers of all wild type core and S1161 transgenic lineages remained largely histologically normal. However, the livers of the S99Q transgenic mice showed significant high level of cell dysplasia associated with the transgene expression in hepatocytes largely located around the central veins by in situ hybridization analysis. In conclusion, the mutant HCV core protein at S99Q may contribute to the progress of HCV induced liver disease.