Following preliminary reports of small studies that suggested a clinically important enhanced benefit from combination therapy with interferon-alpha (IFN) and ribavirin over IFN monotherapy in chronic hepatitis C, a meta-analysis of data from these studies was performed to estimate the efficacy and tolerability of combination therapy in chronic hepatitis C. Records were obtained from 59 patients who had received combination therapy with IFN 3 MU three times weekly and ribavirin 1000-1200 mg daily for six months and were followed for six months after stopping combination therapy. Outcome measures included the percentage of patients showing ALT normalization and HCV-RNA negativity six months after therapy (sustained response) and the percentage of patients stopping therapy because of side effects. Sustained response was observed in 21% of IFN nonresponders and in 60% of patients who had relapsed after IFN. For naive patients, the estimated sustained response rate was 52%; the observed response rate was 46%. No serious adverse effects were noted; less than 10% of patients discontinued study medication. This meta-analysis of IFN-ribavirin combination therapy for chronic hepatitis C suggests that combination therapy results in a two- to threefold greater efficacy than IFN monotherapy, whereas side effects are similar to IFN monotherapy, with the exception of ribavirin-induced anemia. Interferon-ribavirin combination therapy might become the next step in antiviral therapy for chronic hepatitis C.