From among of six strains of Lactobacillus able for production of lactic acid in whey medium, the strain of Lactobacillus delbrueckii sp. bulgaricus s/l was chosen for further experiments as most suitable one. The effect of inoculum concentration and the composition of the medium on the production of lactic acid were studied. It was found that for the inoculation of the medium, 10% (v/v) of the inoculum of propagation lasting 18 h, in the medium MRS containing lactose, should be applied. The amount of lactic acid obtained varied from 3,1 to 7,1 g/100 ml medium, depending on the composition of the medium. Produced L(+) lactic acid constituted over 95% of the sum of D and L isomers. When whey was supplemented with yeast autolisate, lactic acid production and yield process increased. The maximum yield of lactic acid production (97,3%) was obtained when L. delbrueckii sp. bulgaricus s/l was cultured for 44 h in the temperature of 43oC in medium containing whey enriched with 5% of yeast autolisate and 6% of CaCO3.