The efficacy using a 24-week combination therapy in the sustained clearance of serum HCV RNA is equivalent to that using a 48-week combination therapy in patients with HCV genotype non-1 [Hadziyannis et al, EASL 2002]. A 48-week course of pegylated IFN and RBV combination therapy, in contrast, has been shown to yield a better efficacy in the sustained clearance of serum HCV RNA in patients with HCV genotype 1 than a 24-week combination therapy in western countries [SVR: 40~51% vs. 29~41%, Table 1, Hadziyannis et al, EASL 2002; Poynard et al, 1998]. Based on these findings, NIH Consensus Statement suggests that patients with genotype 1 need 48 weeks of combination treatment and standard doses of RBV [NIH 2002]. Previous study revealed that a 12-week RBV therapy was not effective for patients with chronic hepatitis B [Kakumu et al, 1993]. Therefore, in this proposal, the treatment duration will be 24 weeks for HCV genotype 2/3, and will be 48 weeks for HCV genotype 1, in patients with monoinfected chronic hepatitis C and dual chronic hepatitis C and B.