The influence of the pasteurization of milk in a temperature of 72°, 76° and 84 °C for 15 secs on its microflora has been determined in laboratory experiments. Special attention was drawn to heat-resistant bacteria. It was observed that the temperatures used in the experiments have different bactericidal efficacy. From among the various physiological groups of bacteria under test, heat-resistant bacteria proved to be tha least sensitive to heating. Identification showed that the latter group of bacteria was dominated by those belonging to the genera of Bacillus and Microbacterium.