To study the effects of monotherapy with leucocyte interferon-alpha (IFNalpha) versus IFNalpha + ribavirin in patients with chronic hepatitis C who were nonresponders to previous courses of recombinant or lymphoblastoid IFNalpha. This was a nonblind randomised study of outpatients at 3 centres in Palermo, Sicily, Italy. We recruited 72 patients (48 males, 24 females), mean age 48.8 +/- 6.6 years (range 31 to 63 years), with biopsy-proven chronic hepatitis C, predominantly genotype 1b. 24 patients (group A) received IFNalpha 6MU 3 times weekly for 6 months, and 48 patients (group B) received IFNalpha 6MU 3 times weekly + ribavirin 1200 mg/day for 6 months. ALT levels and adverse effects were monitored monthly, and hepatitis C virus (HCV) RNA levels were measured at study entry, at the end of treatment and after a 6-month follow-up. At baseline all patients were HCV-RNA positive and had ALT levels greater than twice normal. Mean post-treatment serum HCV-RNA levels were below baseline in group A, but the virus was eradicated in only 1 patient; 6 patients had normalised serum ALT levels. In group B at end of treatment, 12 patients were negative for HCV-RNA and serum ALT levels were normal in 18. At follow-up, all group A patients had elevated ALT levels and positive HCV-RNA. In group B, 3 patients were still negative for HCV-RNA and 4 had normal ALT. In 4 patients in group B, therapy was suspended because of anaemia, depression and decrease in neutrophil count; a flu-like syndrome was recorded with no frequency difference between groups. These results suggest that patients with chronic hepatitis C unresponsive to IFNalpha monotherapy could benefit from combination therapy with IFNalpha + ribavirin.