Wild propionibacteria isolated from different commercial swiss cheese samples were tested for antimicrobial activities. In initial screening, six of these Propionibacterium isolates showed antagonistic activity against 10 selected indicator organisms by the deferred method. In next, only two Propionibacterium strains JW6 and JW14 showed antibacterial activity in the cell-free supernatants by the modified well diffusion method. Propionibacterium strains JW6 and JW14 were finally identified as bacteriocin producers which exhibited a bactericidal effect against closely related species. The antimicrobial substances were proteins, since their activities were completely destroyed following several degradative enzyme treatments. The bacteriocins showed a narrow inhibitory spectrum of activity against two propionibacteria and two bacilli of strains tested in this study.