The mechanism by which Hepatitis C virus(HCV) infection promotes the development of hepatocellular carcinoma(HCC) is not known exactly. HCV related HCC occurs frequency in the patients with cirrhosis. There have been reports indicating that Th2-type cytokines down-regulated antitumor immunity, and the activation of type 1 T cell responses produced antitumor immunity. We thought Th1/Th2 imbalance in HCV-related liver cirrhosis might be closely related to the development of HCC. In this study, therefore, we investigated the Th1/Th2 balance at the single lymphocyte level of the patients with HCV-related liver cirrhosis and compared with normal controls by using flow cytometry. Th1-type cytokines(IFN-gamma, IL-2) production was significantly decreased in patients with cirrhosis, whereas Th2-type cytokine production(IL-10) was increased. These suggest Th1/Th2 imbalance in HCV-related cirrhosis would decrease the antitumor immunity and its improvement might present the protective effect from HCC.