Abstract Background: The most effective current therapy for hepatitis C virus (HCV) infection is the combination of pegylated interferon (peg-IFN) plus ribavirin (RBV). Objective: The aim of this retrospective analysis was to determine the rateof response to this therapy, and the factors affecting outcome, in patients with treatment-refractory chronic HCV genotype l b. Methods: The records of patients with chronic HCV infection and HCV geno-type1b who failed (nonresponse or relapse) previous treatment with standard interferon (IFN) + RSV were retrospectively analyzed for demographic data, virologic load, liver histology, biochemistry, treatment-related adverse effects (AEs), and the effects of dose reduction during treatment with peg-IFN + RBV for 48 weeks. Early virologic response (EVR) was defined as ≥2-log (copies/mL) decrease from baseline in serum HCV RNA concentration or the absence of detectable serum HCV RNA at treatment week 12. End-of-treatment response (ETR) was defined as the absence of detectable serum HCV RNA at treatment week 48. Sustained virologic response (SVR) was defined as the absence of detectable serum HCV RNA 24 weeks after treatment was discontinued. Factors affecting treatment outcome were determined using correlation analyses. Results: Data from the files of 17 patients (12 men, 5 women; mean [SD] age, 48  years) were analyzed. EVR was achieved in 7 patients; however, viral breakthrough occurred in 2 of these patients during the treatment period, and 5 of these patients discontinued treatment because of severe treatment-related AEs (depression [1 patient] and neutropenia ). Seven patients achieved ETR, but HCV infection relapsed during the follow-up period. Three (18%) patients achieved SVR. Data concerning previous patterns of response to IFN + RBV therapy were available in 10 patients. Of these, 3 of 6 patients who had experienced relapse with the previous treatment achieved SVR with peg-IFN + RBV; neither of the 2 patients with nonresponse to the previous treatment achieved SVR. Major determinants of failure to reach SVR in these patients included previous nonresponder pattern, noncompliance with the therapy, and advanced-stage liver fibrosis. Tolerability was similar to that with the previous treatment. Conclusions: In this study in patients with chronic HCV genotype lb infectionand a history of relapse or nonresponse to standard IFN + RSV treatment, treatment with peg-IFN + RBV achieved an SVR rate of 18%. Further research is needed to determine the role of peg-IFN + RBV in the re-treatment of HCV infection.