Treatment of chronic hepatitis C with alfa interferon for 6 months achieves sustained responses in 15-25% of the patients. The initial induction with higher doses and the prolongation of treatment can improve the results. A randomized, prospective study was carried out to compare the efficacy of a short term induction schedule of interferon alfa-2b (group A) versus a long term one (group B). 106 patients with chronic hepatitis C were included: 54 received 5 megaunits tiw for 8 weeks and 52 for 16 weeks; afterwards, interferon was reduced to 3 megaunits up to 9 months. The percentage of sustained responses, transient responses and non responses were 18.5%, 24% and 57.4% in group A and 23.1%, 28.8% and 48.1% in group B (NS). The following factors were related to a poor response in the univariate analysis: an increase of serum iron levels, ferritin, Gamma-GT and bilirubin, anti-nuclear antibody positivity, presumed non-parenteral infection, an AST/ALT ratio greater than 0.75, a higher Knodell's index and a greater necrosis and fibrosis score. The multivariate analysis revealed that elevated serum iron and ferritin and anti-nuclear antibody positivity had an independent predictive value related to a non response. Our results appear to suggest that an induction with higher doses and the treatment over nine months are more efficient than the classic schedule. The prolongation of the induction period does not provide additional advantages.