The aim of this randomized prospective study was to assess the efficacy and safety of a triple therapy with interferon-alpha (IFN-alpha)-ribavirin-interleukin-2 (IL-2) for the treatment of patients with genotype 1 infection and high viral load nonresponsive to primary IFN-ribavirin therapy. Twenty hepatitis C virus (HCV) genotype 1 patients with high viral load and Metavir fibrosis score >or=2 without HIV co-infection who were previously nonviral responders to standard treatment with IFN plus ribavirin were intensively re-treated with IFN-alpha2a (3 millions (M) IU every 2 days) combined with ribavirin (1000-1200 mg/day) for a 24-week period. Patients were randomized to receive four cycles of subcutaneous injection of IL-2 (3 MIU/day, 5 days a week every 3 weeks) during either the first 12 weeks (group 1, n = 10) or the last 12 weeks (group 2, n = 10) of combination therapy. At the end of triple therapy, six patients (30%) achieved a biochemical response and 4 (20%) a viral response followed by a relapse after triple therapy withdrawal. After 12 weeks of therapy, no difference in viral load was observed between the groups. The decrease in viral load in group 2 was not raised after the addition of IL-2 to IFN plus ribavirin combination therapy. No serious adverse effects were observed. In conclusion, in patients with poor predictive factors of response, the addition of IL-2 to IFN ribavirin combination therapy does not exert a favourable impact on HCV treatment.