This experiment was to investigate the Leptospiral antibody in the pigs with the serological test by the microscopic-agglutination-test (MAT) from November 1991. to Januaury 1992. Antigen(living antigen) was used L. icterohemorrhagiae, L. pomona, L. canicola, L. hardjo, L. ballum, L. australis, L. autumnalis, L. grippotyphosa, L. tarassovi, L. pyrogenes, L. bataviae, L. hebdomadis for the serolgical test in the pigs. The result obtained are summarized as follows of the total 202 serum samples examined, 1. Among the serum samples of 202 heads, 19 heads of the pigs(9.4%) were positive. 2. Among the positive samples of 19 heads, The detected were L. icterohemorhagiae 10 heads(5.0%), L. pomona 3 heads(1.5%), L. canicola 6 heads(3.0%). 3. Antibody titers of positive sera were ranging from 1：100 to 1 : 400. Serotiters appeared to be very low, 4. The seroprevalence of Leptospira in Chechon was higher than that other districts (5. 4% -5.8%), but the lower than Chung-nam, Kyonggi(13.7-15.9%)