Background/Aims: The standard treatment for chronic hepatitis C infected with HCV genotype-1 is a combination of pegylated interferon alfa and ribavirin for a 48weeks. It is unclear if 24weeks treatment is possible for patients showing a rapid virologic response (RVR) without compromising the sustained virologic response (SVR) in Korea. Method: Between June 2005 and July 2008, among patients chronically infected with the HCV genotype-1 (HCV-1) who were treated with pegylated interferon alfa subcutaneously once weekly plus ribavirin (weight-based), 20 consecutive paients who had low pretreatment viral load ( 1.5x10 6 copies/mL) and RVR were treated for 24weeks and then followed up for 24weeks. The HCV RNA was quantitatively assessed pretreatment, at 12weeks of treatment and was qualitatively assessed at 4weeks of treatment, the end of treatment (24weeks), 24weeks after end of treatment. RVR was defined as undetectable HCV RNA at the 4weeks. Results: Baseline characteristics of patients was as followed; age (30-65years:mean 45years), BMI (21-27kg/m²:mean 23.5kg/m²), HCV RNA titer (0.3-1.4×10 6 copies/mL:mean 0.5×10 6 copies/mL), ALT (5-751IU/L:median 77IU/L). Among the 20 patients, all patients (100%) had sustained virologic response (SVR). Conclusions: HCV-1 infected patients with a low baseline HCV RNA concentration ( 1.5×10 6 copies/mL) who had HCV RNA negative at week 4 of treatment may be treatment for 24weeks without compromising sustained virlolgic response. However, an additional trial will be needed to optimize the treatment duration. 