The purpose of our study was to determine the species composition of microflora and to study its sensitivity to antibiotics for toxic osteonecrosis of the jaws, depending on the phase of the inflammatory process to develop the principles of rational antibacterial therapy of this pathology. The Methods. A retrospective study of 38 patients aged from 21 to 45 years old, observed in the dental clinic of PSMU from 2012 to 2018, including 25 men and 13 women, was conducted. They were divided into 2 groups. The first group (19 people) were admitted for emergency treatment in the acute phase of the inflammatory process, accompanied by the development of pyo-inflammatory complications in the maxillofacial area. The second group (19 people) were hospitalized as planned for sequestrectomy. Bacteriological research from a pathological focus was carried out with all of the subjects, followed by determination of the sensitivity of the selected microflora to antibiotics. The rezults. After analyzing the results, it turned out that differences in the composition of the predominant microflora were revealed in the different study groups: in the group of patients with osteonecrosis in the acute phase, the prevailing group of bacteria were staphylococci, in the group of patients with osteonecrosis in the chronic phase - streptococci. In addition, in the first group, the presence of such microorganisms as enterococci and acinetobacter was noted, and in the second group, bacilli and fungi. Also, the isolated microorganisms in the first group were more susceptible to antibiotics than in the second. At the same time, it is preferable to use levofloxacin and gentamicin in both study groups. In addition, penicillin preparations, cephalosporins and chloramphenicol can be used in the acute phase. Summary. This study showed that the composition of microflora in toxic osteonecrosis is diverse and depends on the phase of the inflammatory process. It is the basis for the appointment of a rational antibacterial therapy, which contributes to more successful treatment of this disease, reducing the risk of developing severe purulent complications and generalizing the inflammatory process.