Objective To evaluate the efficacy and safety of therapy for patients with histologically mild hepatitis C virus (HCV) liver disease. Design A randomized, double blind, placebo controlled trial of interferon alpha-2b with or without ribavirin. Setting Regional and university hospitals. Participants One hundred and sixteen treatment naive patients with mild chronic HCV infection. Mild HCV infection was defined according to Knodell as a grade score of greater than or equal to1 and less than or equal to6 and a stage score of less than or equal to1. Interventions Interferon alpha-2b (3 MU three times weekly) for 52 weeks in combination with either ribavirin or a matched placebo. Main outcome measures The study endpoint was the absence of HCV RNA in plasma and liver tissue 26 weeks post-treatment. In addition, liver histology was compared pre- and post-treatment. Results Combination therapy was superior to interferon monotherapy, with a virological sustained response rate of 54% (31/57) and 20% (12/59), respectively, in both serum and liver tissue (p = 0.001). The sustained response rate was higher with combination therapy than monotherapy both in genotype non-1 (81% vs 36%) and in genotype 1 (28% vs 4%). There was a significant improvement in mean grade score in all sustained responders, irrespective of treatment arm. Conclusion Combination therapy with interferon and ribavirin was safe and as effective in patients with histologically mild HCV infection as previously reported for more advanced disease. Eur J Gastroenterol Hepatol 14:627-633 (C) 2002 Lippincott Williams Wilkins.