Twenty isolates of Hantavirus were isolated from patients and reserovirs from 1988 to 1994 in Korea. Isolation rate was 1.9% (10/538) in patients, 6.2% (5/81) in Apodemus sp., 2.6% (1/38) in Rattus sp. and 0.6% (4/677) in bats. Reciprocal mean IFA titers ranged from 27.5 to 1,024 at the specimen collection. According to the growth rate and reaching peak titier of infectivity, the isolates were grouped as rapid, intermediate, and slow growing groups. All isolates were confirmed as Hantaan type by the nested RT-PCR on the G1 region of the M segment. Comparison of nucleotide sequence (Nt: 2101 - Nt: 2280) of the G2 region revealed that the sequence homology bewteen Hantaan 76/118 virus and the isolates was more than 90%. Several nucleotide positions of the isolates showed high variation. The variation rate of patientisolates was about one-half when compared with that of rodentisolates. On the basis of phylogenetic analysis Hantaan viruses isolated were divided into two genogroups. These results indicate that Hantaan virus is highly dominant serotype in Korea and the virologic property and genogroup are not correlated.