The effect of three individual strains of Lactobacillus (L. acidophilus NCC 12, L. acidophilus NCC 36, L. acidophilus NCC 68)and two Bifidobacterium strains (B. bifidum Bb13, B. bifidum NCC 381) on the growth and AFB1 production of Aspergillus flavus NRRL 2999 was determined. The commercial MRS broth and skim milk medium were used to determine the effect of tested bacteria on the growth and AFB1 production of A. flavus NRRL 2999. The bacteria were not effective in preventing the growth of A. flavus NRRL 2999 both in MRS broth and skim milk. However, higher levels of AFB1 were obtained in the presence of individual strains of Lactobacillus and Bifidobacterium. The greatest difference was observed in the AFB1 production of A. flavus NRRL 2999 in skim milk medium compared with MRS broth.