Fifty-four Pectobacterium carotovorum subsp. carotovorum strains isolated in Korea were characterized by a spectrum of antibacterial activities against 7 indicator strains chosen to represent various regions and host plants. All P. carotovorum subsp. carotovorum isolates tested could be grouped into 4 classes depending on the pattern of antibacterial substance production. All tested strains had DNA fragment(s) homologous to the genes encoding carotovoricin and 21 of them had genes homologous to DNA invertase. Sixteen strains had genes homologous to the genes encoding carocin S1. Several isolates produced antibacterial substances active against strains in Brenneria, Pantoea, and Pectobacterium genera that belonged formerly to the genus Erwinia. Strains in Pseudomonas or Xanthomonas sp. were not sensitive to the antibacterial substances produced by P. carotovorum subsp. carotovorum, except for X. albilineans that was sensitive to antibacterial substances produced by most strains in P. carotovorum subsp. carotovorum and P. betavasculorum KACC10056. These results demonstrated the diverse patterns of antibacterial substance production and the possibility of the existence of new antibacterial substance(s) produced by P. carotovorum subsp. carotovorum isolated in Korea.