We have evaluated the efficacy of interferon-alpha (IFN-alpha) plus zinc therapy in hepatitis C patients with genotype 1b, poor responders for IFN alone. Ten patients were injected with 10 MU of IFN-alpha every day for 4 wk, followed by three times a week for 20 wk (control group). Nine patients took 300 mg of zinc sulfate a day orally during IFN-alpha therapy (zinc sulfate group), and 15 patients took IFN-alpha and 150 mg of polaprezinc (polaprezinc group). On the d 8 of IFN therapy, circadian zinc levels in serum elevated significantly in the polaprezinc group compared to the zinc sulfate group or control group. Serum ALT levels normalized in 73.3% of the polaprezinc group, 55.6% of the zinc sulfate group, and 40.0% of the control group at 6 mo after the end of IFN therapy. Sustained eradication for the hepatitis C virus RNA judged at the end of the 6-mo follow-up period was higher in the polaprezinc group than in the zinc sulfate group (53.3% vs 11.1%, p < 0.05) or the control group (20.0%). No clinical side effects of zinc were observed at the dose used. The data suggest that polaprezinc is expected to increase the therapeutic response of IFN-alpha for chronic hepatitis C with genotype 1b.