Background & Aims: Inadequate data are available about retreatment of nonresponders to interferon (IFN) and ribavirin. Thus, this study evaluated the efficacy and tolerability of a 48-week therapy with pegylated IFN-α-2b plus high-dose ribavirin in patients who have failed to respond to the combination. Treatment up to 48 weeks also in patients who have failed to clear hepatitis C virus (HCV) RNA by week 24 was also evaluated. Methods: One hundred forty-one patients who previously did not respond to IFN and ribavirin, 86% with genotype 1 or 4 infection, 52% with high viral load (>800.000 IU/mL), 22% with cirrhosis, were retreated with pegylated IFN-α-2b 1.5 μg/kg per week and ribavirin 1000–1200 mg/day for 48 weeks and followed up for 24 weeks. Results: By intent-to-treat analysis, 20% of patients achieved a sustained virologic response (SVR). SVR of genotype 1 patients was 19%. Independent predictors of SVR were low γ-glutamyltransferase levels (OR, 22.9; 95% CI: 6.6–79.6) and low viral load (OR, 3.8; 95% CI: 1.1–12.6). Twelve (23%) out of 51 patients who were HCV RNA positive after 24 weeks of therapy achieved a late virologic response (after week 24) and 5 (10%) of them, all with genotype 1, achieved an SVR. Genotype was not associated with response (P = .2) or with early response (P = .3). Conclusions: Retreatment with pegylated IFN-α-2b and ribavirin of multiexperienced and “difficult to treat” nonresponder patients produced a very promising SVR. Accurate selection of patients, such as those with low viral load and low γ-glutamyltransferase levels, and prolongation of therapy beyond 24 weeks also in HCV RNA-positive patients may further increase the rate of SVR.