The study on leptospiral infection among cows was carried out to find out possible role of this domestic animal as an infection source for humans, and the magnitude of economic loss due to abortions caused by leptospiral infections among the domestic animal. Bood samples of 459 cows in May and 446 heads in November 1989 were collected from 19 villages of Kyunggi Province. These samples were cultured and serologically tested. Only one strain of leptospires, most strongly reactive to Pomona antibody, was isolated from duplicated cultures of 985 cow blood samples in EMJH medium. Serological test by MAT with seven reference strains and three locally isolated strains was positive in 12% of the sample in May and 26% in November ; positive rate increased slightly as the age of cows increased and male cows had higher positive rate, however, there was on difference in positive rate by type of cow and area. There was no statistically significant association between abortion history among cows(one yearperiod) and positive MAT. Thus it was concluded that the leptospiral infection of cows may play a role for human infection, and the leptospiral infection of cow may not be the major cause of abortion although further study is necessary for definite conclusion.