The article presents the results of research into the therapeutic effect of hyperbaric oxygenation on bacterial infections performed on an animal model. The studies were performed on Porton mice infected intraperitoneally with haemolysing streptococci and later subjected, over a 3-day period, to 5 exposures of hyperbaric oxygenation at a pressure of 2.8 ata. Depending on the research group, the treatment was commenced after 24, 48, 72 and 96 hours from the moment of infection. Some of the animals died during the experiment.8 and 12 days from the date of infection, selected animals of each group were put to death and subjected to post mortem examination. A statistically significant positive effect of hyperbaric treatment on the survival rate, as well as on the development of complications (liver abscesses), was observed in those animals where the hyperbaric oxygenation was applied at an early stage. In groups where the therapy was initiated later, no positive effect was noted, and the complications tended to develop more rapidly.