Objective. Identification of causes and risk factors of mortality of socially significant co-infections Methods. Epidemiological аnаlisis of mаteriаls registration of coinfection аnd klinico-epidemiologicаl dаtes Results. The growth of the morbidity and at the same time reducing mortality from socially significant co-infections in St. Petersburg was revealed. The main cause for the increase in morbidity is the growing epidemic potential of tuberculosis, HIV infection and viral hepatitis in past years. Lethal outcomes mainly occur in the terminal stage of the disease, accompanied by high viral load and severe immunosuppression. Highest mortality rate (80-100 %o) was observed in case of generalized tuberculosis and multiple organ lesions of internal organs. The factors of adverse outcomes are drug use, alcohol use, refusal of tuberculosis and antiretroviral therapy. Conclusions. Improving the interaction and combining the efforts of specialists of different profiles is advisable on the basis of a single register of socially significant co-infections, which includes all the components of the integration of the epidemic process: tuberculosis, HIV infection, viral hepatitis B, C and D as the single infection, and in their combination.