Recently, T-Kohara et al. reported that most hepatitis C virus (HCV) in Japan can be classified into two groups, group 1 (G-1) and group 2 (G-2), on the basis of the NS4 region nucleotide sequence. Using a genetic engineering method, they developed a new assay in which antibodies against group specific recombinant proteins of the NS4 region were measured by ELISA (Serological Genotype, Serotype). In the present study, we examined 100 patients with chronic liver disease due to hepatitis C. The sensitivity of this assay was 98.0% (98/100). The HCV serotype distribution was 74/100 (74.0%) for serotype G-1, 22/100 (22.0%) for serotype G-2, 2/100 (2.0%) for both being positive and 2/100 (2.0%) for indeterminate. The distribution of G-1 was significantly higher than that of G-2 (p < 0.05), however, we found no difference between the distribution of G-1 and that of G-2 in age, sex, history of blood transfusion or type of liver disease. In the same serum samples, we performed HCV genotyping by reverse transcription polymerase chain reaction (RT-PCR) using type specific primers derived from the NS5 region of HCV to verify the specificity of such serotyping. The sensitivity of genotyping by RT-PCR was 88.0% (88/100). The HCV genotypes determined by both methods were consistent in 86.0% (86/100) of cases, and were not contradictory in any sample. These data indicated that serological genotyping was more sensitive and was consistent with genotyping by RT-PCR. Therefore, we consider the method useful for epidemiologic studies of HCV in Japan.