Streptococcus(Str.) dysagalactiae known as the causative agent of environmental mastitis were isolated from the raw milk and environmental specimens of the 9 dairy farms located in Kyunggido, Korea. Genotyping by PFGE analysis of SmaI digested genomes and by RAPD have been conducted in order to elucidate the contamination route into raw milk, and their susceptibility against 19 antibiotics were determined. Str. dysagalactiae could be detected in 58 samples of 572 samples. In strain typing PFGE was more discriminatory method than RAPD revealing 11 genotypes for 22 strains studied, RAPD yielded 7 genotypes. Str. dysagalactiae found in milk samples were originated from the environmental sites and animal body. High degree of heterogeneity in genotype and in antibiotic resistance revealed and even strains have identical genotypes showed different chloramphenicol and vancomycin resistance. Each genotypes of Str. dysagalactiae revealed typical pattern of antibiotic susceptibilities. Minimum inhibitory concentration of chloramphenicol against Str. dysagalactiae turned out to be 50㎍/㎖.