Sustained virological response (SVR) to antiviral therapy in patients with chronic hepatitis C genotype 1 according to subtype (1a vs.1b) has not been extensively investigated. This observational study was carried out on a large group of "naïve" HCV patients to evaluate difference, if any, between HCV genotype 1 subtype 1a and 1b on the response to treatment with peginterferon (Peg-IFN) plus ribavirin.