BACKGROUND: The combination therapy of pegylated-interferon-alpha2a plus ribavirin is considered as the standard of care for patients with chronic hepatitis C. A sustained viral response is obtained in 40-50% of naïve patients with genotype 1 and in around 80% of naïve patients with genotype 2 or 3. AIM: To assess whether amantadine, added to the conventional combination therapy, could improve the treatment efficacy. METHODS: In all, 630 patients (intent-to-treat population) with chronic hepatitis C were randomized into two groups: 316 patients (treatment group) received pegylated-interferon-alpha2a (180 microg once weekly) plus ribavirin (1000-1200 mg/daily) with amantadine (200 mg/daily); 314 patients (control group) received pegylated-interferon-alpha2a (180 microg once weekly) plus ribavirin (1000-1200 mg/daily) without amantadine. The duration of the treatment was 48 weeks for genotypes 1, 4, 5 and 6, and 24 weeks for genotypes 2 and 3. RESULTS: There was no statistically significant difference between treatments groups for any of the variables tested for. Subgroups of patients likely to take advantage of the addition of amantadine were not identified. CONCLUSIONS: This large study definitely excludes the role of amantadine in addition of conventional combination therapy in the treatment of chronic hepatitis C patients.