The authors investigated the distribution of HCV genotypes in patients with various chronic liver diseases in Korea. Study population was 70 individuals, positive for second generation anti-HCV EIA, consisting of 37 cases with sporadic non-A, non-B (NANB) chronic hepatitis (CH), 12 NANB hepatocellular carcinoma, 16 post-transfusion NANB hepatitis, 4 non-B blood donors and 1 healthy family member of a patient with sporadic CH. Molecular typing was performed by RT-nested PCR with type-specific primer sets deduced from the NS-5 region of HCV. The prevalence of type II was 75.0% and type III was 25.0% in sera. In liver tissues, type II HCV was shown in 63.0%, type III HCV in 3.7% and co-infections with type II and III HCV were observed in 18.5% of 27 samples biopsied. In the sera of patients with chronic hepatitis, typing results were relatively well correlated with those in tissues (75%), but type III could not be observed. Among 12 HCC patients, type III HCV appeared only in tissues, not in sera. These results suggest that type II HCV may be the major HCV type in Korea, and co-infections with type II and-III HCV may not be rare in chronic liver diseases with HCV.