AIM: To evaluate the impact of hepatitis C virus (HCV) infection with genotype 1 or 3 and the presence or absence of liver cirrhosis (LC) in the early viral kinetics response to treatment. METHODS: Naive patients (n = 46) treated with interferon-α (IFN-α) and ribavirin and followed up with frequent early HCV-RNA determinations were analysed. Patients were infected with genotype 1 (n = 28, 7 with LC) or 3 (n = 18, 5 with LC). RESULTS: The fi rst phase decline was larger in geno- type 3 patients than in genotype 1 patients (1.72 vs 0.95 log IU/mL, P < 0.001). The second phase slope decline was also larger in genotype 3 patients than in genotype 1 patients (0.87 vs 0.15 log/wk, P < 0.001). Differences were found in both cirrhotic and non-cirrhotic patients. Genotype 1 cirrhotic patients had a slower 2nd phase slope than non-cirrhotic patients (0.06 vs 0.18 log/wk, P < 0.02). None of genotype 1 cirrhotic patients had a 1st phase decline larger than 1 log (non-cirrhotic patients: 55%, P < 0.02). A similar trend toward a slower 2nd phase slope was observed in genotype 3 cirrhotic pa- tients but the 1st phase slope decline was not different. Sustained viral response was higher in genotype 3 pa- tients than in genotype 1 patients (72% vs 14%, P < 0.001) and in genotype 1 non-cirrhotic patients than in genotype 1 cirrhotic patients (19% vs 0%). A secondphase decline slower than 0.3 log/wk was predictive of non-response in all groups. CONCLUSION: Genotype 3 has faster early viral decline than genotype 1. Cirrhosis correlates with a slower 2nd phase decline and possibly with a lower 1st phase slope decline in genotype 1 patients. AIM: To evaluate the impact of hepatitis C virus (HCV) infection with genotype 1 or 3 and the presence or absence of liver cirrhosis (LC) in the early viral kinetics response to treatment. METHODS: Naive patients (n = 46) treated with interferon-α (IFN-α) and ribavirin and followed up with frequent early HCV-RNA determinations were analyzed. Patients were infected with genotype 1 (n = 28, 7 with LC) or 3 (n = 18, 5 with LC). RESULTS: The fi rst phase decline was larger in geno- type 3 patients than in genotype 1 patients (1.72 vs 0.95 log IU / mL, P <0.001). The second phase slope decline was also larger in genotype 3 patients than in genotype 1 Patients with genotype 1 cirrhotic patients had a slower 2nd phase slope than non-cirrhotic patients (0.06 vs. 0.18 log / wk, P <0.001) <0.02) None of genotype 1 cirrhotic patients had a 1st phase decrease larger than 1 log (non-cirrhotic patients: 55%, P < 0.02). A similar trend toward a slower 2nd phase slope was observed in genotype 3 cirrhotic pa- tients but the 1st phase slope decline was not different. Sustained viral response was higher in genotype 3 pa- tients than in genotype 1 patients (72% vs 14%, P <0.001) and in genotype 1 non-cirrhotic patients than in genotype 1 cirrhotic patients (19% vs 0%). A secondphase decline slower than 0.3 log / wk was predictive of non-response in all groups. CONCLUSION : Genotype 3 has faster early viral decline than genotype 1. Cirrhosis correlates with a slower 2nd phase decline and possibly with a lower 1st phase slope decline in genotype 1 patients.