Persistent infection of hepatitis C virus (HCV) can lead to a high risk for hepatocellular carcinoma(HCC). HCV core protein plays important roles in HCV-induced hepatocarcinogenesis, because its expression in mice causes hepatic steatosis and HCC without accompanying hepatitis. However, its precise mechanisms remain unclear. We investigated whether the HCV core protein alters the expression of the factors associated with hepatic steatosis and HCC in vivo. By Western immunoblot and Northern blot analyses, expression of the proteins including fatty acid-metabolizing enzymes and cell cycle regulators, which are induced by the activation of peroxisome proliferator-activated receptor alpha (PPARalpha), significantly increased in HCV core protein transgenic mice. This result suggests the possibility that PPARalpha activation might contribute to HCV core protein-mediated hepatocarcinogenesis.