Hantaan virus is widely distributed in Korea and has been known to cause hemorrhagic fever with renal syndrome (HFRS). Hantaviruses are carried by numerous rodent species throughout the world. Especially, the striped field mice, Apodemus agrarius, is natural host for Hantaan virus in Korea. In this study, a total 105 wild rodents of 3 species (101 of Apodemus agrarius, 2 of Eothenomys regulus, and 2 of Mus musculus) were trapped in Kyonggi and Gangwon provinces for April to June, 2001 to study serologic and genetic characterization. 8 Apodemus agrarius (7.9%) were immunofluorescent antibody (IFA) positive against Hantaan virus and Hantaan virus genome was found in 5 among 8 seropositive rodents. S gene of isolated Hantaan virus genome was amplified and directly sequenced. Based on 917 bases of S gene (411-1327 bases), 2001 Korean isolates showed 94.8% to 95.5% nucleotide homologies in comparison with prototype Hantaan virus 76-118 which was isolated from Apodemus agrarius in Korea, 1976. The partial M gene (1969-2240 bases) showed 94.1% to 100.0% nucleotide homologies in comparison with 76-118 strain. In phylogenetic analysis, 2001 Korean isolates made the distinct cluster. Therefore, Hantaan viruses isolated in 2001 were not significantly changed in genetic level comparison with previous isolate from Korea.