The aim of this study was to evaluate rapid virologic response (RVR) rate after peginterferon (PegIFN) and ribavirin (RBV) dual combination therapy in Korean hepatitis C virus (HCV) genotype 1 patients whose IL28B polymorphism is generally favorable. This study also assessed the value of RVR in predicting sustained virologic response (SVR). Treatment-naïve HCV genotype 1 patients who underwent initial treatment with either PegIFN-α-2a or α-2b and RBV were retrospectively evaluated. From 148 patients, 115 met inclusion criteria for the final analysis. Overall RVR rate was 47.8% and SVR rate was 67.8% (78/115). Positive RVR had the highest positive predictive value (PPV) for achieving SVR, whereas it had the lowest negative predictive value (NPV). Undetectable HCV RNA at treatment week 12, namely complete early virologic response (cEVR), had high PPV as well as high NPV. Factors predisposing SVR were absence of liver cirrhosis and achievement of RVR or cEVR. This study showed RVR rate close to 50% in HCV genotype 1 patients treated with dual combination therapy in the region where favorable IL28B polymorphism is reported to be as high as 90%. Even for the patients who failed to achieve RVR, positive cEVR demonstrated a fair chance of achieving SVR. Copyright © 2013 S. Karger AG, Basel.