Interferon alpha (INF) is routine treatment in patients with chronic hepatitis C. Many controlled investigations were evaluated to establish the optimal schedule of treatment with sustained virological and biochemical response. Recently, multicentre meta-analyses suggest that combination therapy (INF + Ribavirin) was more effective than treatment with interferon alone. The aim of this study was to compare the efficacy of four schedules of antiviral treatment in 445 patients with chronic hepatitis C. Combination therapy (INF + Ribavirin) given for 6 mo. and monotherapy (INF) for 18 mo. were more effective than interferon alone given for 6 mo. Treatment with INF alone for 6 mo. was demonstrated to be insufficient.