Background/Aims. The aim of this study was to estabilish the 'true' therapeutical gain of a combined therapy interferon - ribavirin versus interferon monotherapy in hepatitis C virus infection.Methods. A systematic review of published trials comparing combined treatment (interferon+ribavirin) vs interferon monotherapy, was performed on articles printed from 1991 to 1999.Results. The meta-analysis of retrieved trials showed that ribavirin significantly enhances the sustained response rate to interferon therapy in all types of patients. The results of almost all studies were homogeneous: combined therapy approximately doubles response rates compared to interferon monotherapy. At the end of the treatment, ribavirin increased the rate of viral clearance approximately 22% and the biochemical response of about 31%. The net gain was about 24% for both viral and biochemical response rate after 24 weeks of follow-up.Conclusion. Combined therapy showed a significantly higher efficacy in terms of sustained negativity of viral genome in all classes of patients (naives, relapsers, non-responders) becoming the therapy of choice. Nevertheless, more than about 50% of patients infected by hepatitis C virus show no sustained response to treatment. The whole weight of final data is beared by the major trials all with similar results.