summary. Retreatment of relapser patients with chronic hepatitis C with the standard dose of interferon (IFN) of 3 million units (MU) thrice weekly (tiw) plus ribavirin for 24 weeks achieves a sustained response in 30 and 73% of patients with genotype 1 and 2 or 3, respectively. The aim of this study was to evaluate the efficacy and safety of IFN alpha-2b induction therapy, followed by prolonged treatment with a high dose of IFN alpha-2b plus ribavirin in relapser patients. A total of 119 patients were randomized to receive IFN alpha-2b 5 MU daily (Group A: 59 patients) or IFN alpha-2b 5 MU tiw (Group B: 60 patients) for 4 weeks followed by IFN (5 MU tiw) and ribavirin (1000-1200 mg/day) for 48 weeks in both groups. The primary end point was hepatitis C virus (HCV)-RNA clearance at week 24 after the end of treatment. A sustained virological response (SVR) was achieved in 68 and 60% of Group A and B patients, respectively (P = 0.37). Logistic regression analysis identified genotype 2 or 3 as the only independent factor associated with response, whereas induction regimen and baseline viraemia levels did not affect the response. The overall SVR was 53 and 72% in patients with genotype 1 or 4 and 2 or 3, respectively. In conclusion, induction IFN therapy does not enhance the SVR to a 48-week combination therapy. Our study suggests that relapsed patients with genotype 1 or 4 may achieve significant response rates of approximately 50%, if retreated with 5 MU tiw IFN plus ribavirin for 48 weeks.