Basing on the analysis of 143 cases of odontogenic mediastinitis it is shown that in the structure of acute odontogenic infectious diseases this severe complication accounts for 0.3% of cases. In 80% of the cases it develops on the background of chronic somatic diseases representing 51.7% of cases in the age group from 31 to 50 years. Outcome of mediastinitis depends on time of hospitalization, intensity and time of the treatment. Life span and quality of life of the patients depends first of all upon somatic disease compensation.