Interferon-alpha-based treatment is a standard therapy to cure hepatitis C virus-infected patients. However, the reasons for the failure of interferon-alpha treatment in some patients have not been fully elucidated. We evaluated the differences in the expression levels of various cytokines among patients with and without sustained viral response (SVR). We found that the chemokines (MIG and IP-10) and inflammation-related cytokines (IL-6) were transiently elevated in patients with SVR(+) before interferon-alpha treatment and in the early phase of treatment (week 2), indicating that these cytokines may be related to viral clearance. Furthermore, higher serum levels of Th1 and Th2 cytokines (IL-2, IL-4, IL-5, IL-10, tumor necrosis factor, and IFN-gamma) were observed in SVR(-) than in SVR(+) patients, indicating that they may be associated with ineffective anti-HCV immune response. Our data revealed that the patterns of cytokines varied greatly between SVR(+) and SVR(-) patients before and after IFN-alpha treatment.