Antimicrobial activity of 20 strains of L.acidophilus against important food borne pathogens: E. coli, S. aureus, P. aeruginosa, P. fluorescens, and 2 strains lactic acid bacteria L.acidophilus ATCC 4356 and L.rhamnosus GG ATCC 53105 was estimated. All the L. acidophilus strains revealed inhibition activity against indicator organisms. Eleven strains with highest antagonistic activity were screened from this group of L. acidophilus. Antagonistic activity of L. acidophilus was tested in accordance with five different methods. The best results were obtained with double layer methods and agar slab techniques, which gave good diffusion conditions of antagonistic factors.