Patients with biopsy-proven chronic hepatitis C, who failed to respond to a previous course of either recombinant (rIFN-alpha) or lymphoblastoid (Ly IFN-alpha) interferon-alpha, were randomized to receive either leucocyte (Le) IFN-alpha (patients) or a second course of the same IFN-alpha (controls), to compare the efficacy and safety of these treatment schedules. All patients received the same dose of IFN-alpha as was used during their previous treatment (3 million units (MU) or 6 MU three times weekly) for 6 months. Patients with a normal alanine aminotransferase (ALT) value at month 6 were treated for a further 6 months. All patients were followed-up for 12 months after treatment. A total of 69 patients were enrolled, 44 in the Le IFN-alpha group and 25 in the control group. At the end of the treatment period, 13 of the 44 patients (29.5%) in the Le IFN-alpha group had a biochemical response (normal ALT) and six of 44 (13.6%) patients had undetectable serum hepatitis C virus (HCV) RNA. At the end of the follow-up period, 10 patients (22.7%) had normal ALT values and serum HCV RNA was undetectable in three (6.8%). None of the patients in the control group showed normal ALT values at any time. Genotype 1b tended to be more frequent among non-responders (61 vs 45%): basal gamma-glutamyl transpeptidase (gamma-GT) values were lower in responders than in non-responders (33.3 +/- 11.70 Ul-1 vs 58.4 +/- 33.04; P = 0.01). Le IFN-alpha was well tolerated by all patients. These results support the use of Le IFN-alpha in patients with chronic hepatitis C who are non-responders to a previous treatment with recombinant or lymphoblastoid IFN-alpha.