BACKGROUND/AIMS: We assessed the efficacy and safety of pegylated interferon (peginterferon) plus ribavirin and identified the predictors of a sustained virologic response (SVR) in Korean patients with chronic hepatitis C virus infection. METHODS: A total of 192 patients with chronic hepatitis C, treated with both peginterferon (n=141) or conventional interferon (n=51) and ribavirin, were analyzed retrospectively. Peginterferon alfa-2a (180 microgram/week) or -2b (1.5 microgram/kg/week) or interferon alfa-2a (3 MIU thrice weekly) was administered in combination with ribavirin at 1,000-1,200 mg/day for 48 weeks for genotype 1 and at 800 mg/day for 24 weeks for genotypes 2 and 3. RESULTS: The overall SVR rate was 80.9% (114/141) in the peginterferon group and 52.9% (27/51) in the interferon group (P=0.0001). The SVR rate in genotype 1 was 69.5% (41/59) in the peginterferon group and 31.6% (6/19) in the interferon group (P=0.0033), whereas in genotype 2 or 3 it was 89.0% (73/82) in the peginterferon group and 65.6% (21/32) in the interferon group (P=0.0032). The predictors of SVR in the peginterferon group were genotype, absence of cirrhosis, and early virologic response (P<0.05). CONCLUSIONS: In Korean patients with chronic hepatitis C, a regimen of peginterferon and ribavirin was more effective than a regimen of conventional interferon and ribavirin. This result is comparable to those from studies on Western patients as an initial treatment for chronic hepatitis C.