To isolate Bacillus thuringiensis toxic to Spodoptera species, we collected soil samples in Korea. In these samples, we characterized 7 B. thuringiensis isolates toxic to Spodoptera exigua or S. itura from soil, granary and sericultural farm samples. The 7 isolates were named B. thuringiensis STB-1,STB-2, STB-3, STB-4,STB-5, STB-6 and STB-7, respective. The bioassay of these islates against S., exigua and S.litura showed highly insecticidal activity. The serotypes of them were determined by agglutination tests wsing 33 antisera ; STB-1 and STB-2 are identical to B. thuringiensis subsp. Kurstaki, and STB-3, STB-4 and STB-5 are identical to subsp. Kenyae STB-6 and STB-7 did not react with 33 antisera. STB-1 and STB-3 which have different gene types from B. thuringiensis subsp. Kurstaki and subsp. Kenyae are identified new isolates. STB-6 and STB-7 which show no agglutination in serological tests have cryLA(a), cryLA(b), cryIC, and cryII genes are also identified new isolates. Molecular weights of parasporal inclusions of all isolates were determined approximately 130 kDa by SDS-polyacrylamide gel electrophoresis.