We have previously isolated seven strains of spiral form bacteria, which have shown several similar characteristics to Leptospira from patient with epidemic pulmonary hemorrhagic fever and matural paddy water. Further studies have performed to characterize them. All of the isolated bacteria were aerobic, gram negative and spiral form and their growth were completely inhibited at temperature below $13^{circ}C;and;50^{circ}C$. In sensitivity test to drugs, the bacteria were resistant to the bile salts, 5-Fu and Amphotericine B, but sensitive to the 8-Azaguanine. The isolated bacteria as well as 5 serotypes of Leptospira interrogans reacted the patient sera and it was also shown that antisera from rabbit immunized with the isolated bacteria reacted with 5 serotypes of Leptospira interrogans. These results suggest that the isolated bacteria may belong to the genus Leptospira.