The objective of the study was to determine the survival of bacteria of the Lactobacillus genus, included in a probiotic preparation, in a simulated model of the human digestive system. It was proved that those bacteria had a relatively low survival rate in the control sample, i.e. a PBS buffer. The conditions in the simulated gastrointestinal tract caused the logarithmically expressed number of bacteria to decrease from 8.18 to 6.20. The bacteria introduced into the system together with dietary matrices (Nutramigen, nonclarified fruit-vegetable juice, rice gruel) were characterized by a considerably higher survival rate since those matrices formed protective conditions for them. After the matrices were applied, the level of bacterial count maintained to be between 7.50 and 9.00 log units. Although the number of bacteria in the system decreased, what was the effect of low pH value of gastric juice and bile salts therein, the intestinal passage simulated produced very good conditions for bacterial growth. The number of viable cells that reached the light of the large intestine exceeded the count of bacteria at the starting point. In the experiment with Nutramigen, the number of bacteria increased from 8.82 to 9.11 logarithmic units, whereas in the experiment with apple-carrot juice: from 8.46 to 8.86. The protection of Lactobacillus bacteria provided by the rice gruel was much weaker; therefore, it was found that in that experimental system, the initial number of bacteria of 7.85 decreased to the final number of 7.48.