Early virological response (EVR) to different interferon-based regimens plus ribavirin and its ability to predict the outcome of therapy in patients with chronic hepatitis C were investigated. The study design was as follows: 64 naive patients were considered, 32/64 received pegylated interferon alpha-2b (Peg-IFN-alpha2b) plus ribavirin and the remaining 32 received leucocyte interferon alpha (IFN-alpha) plus ribavirin. At week 4 of treatment, EVR was present in 68.7% and 37.5% of patients treated with Peg-IFN-alpha2b plus ribavirin, and with leucocyte interferon alpha (IFN-alpha) plus ribavirin, respectively (p = 0.024). At week 12, the cumulative EVR rates did not differ between the two groups (71.9% vs 56.2%, p >0.05) because a higher proportion of patients achieved EVR for the first time after more than 4 weeks of therapy in the standard IFN-alpha group. Sustained virological response (SVR) rates, however, resulted significantly higher in the Peg-IFN-alpha2b group (65.6% vs 37.5%; p = 0.045) since a higher proportion of patients who received standard IFN-alpha relapsed during the follow-up. In the standard IFN-alpha group, HCV genotype 1 (p = 0.035), high baseline viral load (p = 0.035) and the presence of bridging fibrosis/cirrhosis (p = 0.011) were closely associated with significantly lower SVR rates. In the Peg-IFN-alpha2b group, only bridging fibrosis/cirrhosis (p = 0.02) negatively influenced the outcome of treatment. Overall, 33/41 (80.5%) patients with EVR at week 12 were sustained responders, yielding a positive predictive value (PPV) of 0.80. However, when SVR was related to the time taken to reach EVR, 32/34 (94.1%) patients with EVR at week 4 of therapy (PPV = 0.94) versus 1/7 (14.3%) patients who had EVR after more than 4 weeks of therapy (PPV = 0.14) resulted sustained responders (p = 0.000057). In conclusion, EVR at week 4 of treatment is strongly associated with the likelihood of achieving SVR, regardless of the therapeutic regimen. However, when compared with standard IFN-alpha plus ribavirin, treatment with Peg-IFN-alpha2b plus ribavirin significantly increases the probability of viral clearance within the first 4 weeks of treatment. Finally, patients who do not clear the virus within the first 12 weeks of treatment have no chance of achieving SVR, justifying discontinuation of therapy in these patients.