Korean haemorrhagic fever (KHF) was recognized for the first time in Korea in 1951 during Korean War among United Nations troops in the central front although similar diseases to KHF had been reported as Haemorrhagic nephrosonephritis in Russia, as Epidemic haemorrhagic fever in China, as Nephropathia epidemica in Scandinavia and as Epidemic haemorrhagic fever in eastern Europe and in Japan. In 1976 Lee and Lee discovered the etiologic agent of KHF in the lungs of the striped field mouse, Apodemus agrarius, which gave specific immunofluorescent reaction with sera from patients convalescent from KHF for the first time in Korea. In 1978 Lee et al. Had isolated the same agent from KHF patients sera and had succeeded the propagation of the virus in Apodemus agrarius, and it was named Hantaan virus after Hantaan river. Natural reservoirs of Haemorrhagic fever with renal syndrome are not only field mice and laboratory rats but also wild urban rats. Therefore, we have collected the wild urban rats in the international port of Incheon for serologic survey of Hantaan virus infection and carried out isolation of Hantaan-like virus from infected rats. 1. Among the 215 wild urban rats collected in the international port of Incheon, 112 (52%) had antibodies against Hantaan virus and 51(24%) had Hantaan virus-like antigen. 2. Fourteen strains of Hantaan-like virus were isolated from S.D. rats inculated with the suspension of lungs from 60 wild urban rats. One strain of Hantaan-like virus was isolated from S. D. rats inoculated with the antigen negative lung tissues from 10 urban rats that contained antibodies in the sera against Hantaan virus. In positive urban rats, the largest amount of Hantaan-like virus antigen was distributed in lungs, followed by spleen, liver and kidneys, in that order. 3. 82-3 strain isolated from urban rats in Incheon was cultured in Vero E6 cells, and this virus had antigenicities of both Hantaan and Punmala viruses which cause haemorrhagic fevers in Korea and Scandinavia by immunofluorescent antibody technique. Further study to characterize this Hantaan-like virus is in progress.