Cultural, morphologic, and biochemical characteristics of Lactobacillus casei were studied as well as their acid-forming and antagonistic activity and resistance to antibiotics. 60 cultures identified as L. caseiwere isolated from 250 samples of sour-milk products and clinical specimens. All isolated strains had respectively high antagonistic activity regardless of their source. Dependence between antagonistic activity and acid formation was not detected. Conclusion about promise for using these lactobacilli for manufacturing of probiotics has been done.