INTRODUCTION: Numerous clinical trials have demonstrated the efficacy of treatment with pegylated interferon and ribavirin but little is known about the results obtained in clinical practice. OBJECTIVE: To evaluate treatment response and factors influencing the treatment of chronic hepatitis C in clinical practice. MATERIAL AND METHODS: Between August 2001 and December 2005, we treated 219 patients with pegylated interferon (alpha 2a -fixed dose, or alpha 2b, according to weight) and ribavirin. Patients with genotype 1 or 4 received treatment with pegylated interferon alpha 2a (180 μg/week) and ribavirin (1000 mg/day if body weight was < 75 kg or 1200 mg/day if body weight was > 75 kg) or interferon alpha 2b (1.5 μg/kg/week) and ribavirin (10.6 mg/kg/day) for 48 weeks. Patients with genotype 2 or 3 were treated for 24 weeks with the same regimen of pegylated interferon alpha-2a or alpha-2b, but with 800 mg of ribavirin divided in two daily doses. Sustained viral response was defined as absence of HCV-RNA 6 months after the end of treatment. RESULTS: A total of 219 patients were included (69% men; mean age 44 ± 10). As epidemiological antecedents, 22.4% of the treated patients had previously consumed drugs parenterally and 22.4% had received blood transfusions before 1992. Forty-seven percent of the patients with liver biopsy had fibrosis bridges or established liver cirrhosis. The genotype was distributed as follows: 69.8% genotype 1, 4.1% genotype 2, 17.8% genotype 3, and 8.2% genotype 4. Of the 219 patients, 76 (35%) were treated with pegylated interferon alpha 2a and 143 (65%) with interferon alpha 2b. Analysis of response by genotype revealed that sustained viral response was obtained in 46% genotype 1, 88.9% genotype 2, 78.9% genotype 3, and 33.3% genotype 4. Univariate analysis showed that the only variable influencing sustained viral response was genotype. CONCLUSION: Treatment with pegylated interferon and ribavirin in clinical practice shows a similar pattern of sustained viral response to that obtained in clinical research. The main variable correlated with sustained viral response continues to be viral genotype.