BACKGROUND/AIM: The mechanisms that determine the persistence or clearance of viral infection in patients with chronic hepatitis C (CHC) are not well known. The goal of this study was to clarify changes of the Th1 and Th2 cell subsets of peripheral blood CD4-positive T cells (PB-CD4+Tc) in CHC patients after successful elimination of HCV. PATIENTS AND METHODS: Eighteen CHC patients received natural IFN-alpha at a dose of 5-10MU daily for 2 weeks and three times weekly for 22 weeks, and then were followed for 24 weeks after the completion of IFN therapy (Week 48). Based on the response to IFN, the subjects were divided into two groups: non-responders had detectable serum HCV-RNA at the end of follow-up (Week 48), while responders did not. Before treatment and in Weeks 2, 24, and 48, the intracellular cytokines of peripheral CD4+ T cells were detected by flow cytometry to separate IFN-gamma+/IL-4- (Th1) cells from IFN-gamma-/IL-4+ (Th2) cells. RESULTS: The percentage of Th1 and Th2 cells peaked in Week 2 and then decreased to near baseline by Weeks 24 or 48 in both groups. However, a statistically significant change in the percentage of Th1 cells was only seen in the responders. The baseline percentage of Th1 cells was significantly lower in the responders than in the non-responders, while the percentage of Th2 cells at baseline, Week 24 and 48 was significantly lower in responders than in non-responders. CONCLUSIONS: Our results suggest that the baseline Th1 and Th2 cells may be related to the IFN response to IFN.