The aim of this study was to compare the effects of two different therapeutical regimens of IFN alpha-2a in patients with HCV related chronic liver disease. Eighty one patients with HCV chronic hepatitis with or without cirrhosis entered the study; 42 and 39 patients were treated with 3 or 6 MU IFN, respectively. The results show that: 1) 25/39 (64.1%) patients treated with 6 MU and 21/42 (50.0%) patients treated with 3 MU had a complete response defined as a decline in serum ALT levels to the normal range during therapy; 2) complete response to 6 MU treatment was observed independently of the presence or absence of cirrhosis; in the 3 MU group, a complete response was observed in 31.6% of patients with CAH + cirrhosis as compared with 68.2% of those with CAH alone (p < 0.03); and 3) at 1 year after the end of the treatment we observed persistent ALT normalization in 40.6% and 28.2% of patients treated with 6 or 3 MU, respectively, and absence, of HCV viraemia (HCV-RNA) in 7/10 patients with CAH and in 2/7 patients with CAH + cirrhosis, mostly in patients treated with 6 MU. In conclusion, 6 MU IFN dose is more effective than 3 MU in reducing disease activity in HCV chronic hepatitis, specially in patients with CAH + cirrhosis.