The article presents the results of the analysis of the main trends in the epidemic process for mycoplasmal and chlamydial infections among children with respiratory diseases over several seasons from November 2018 to July 2020 based on the results of testing 617 serum samples. The data obtained indicate that, along with seasonal fluctuations in seropositivity, there is an epidemiological season from December 2019 to January 2020, characterized by a peak increase in the number of seropositive cases, the largest number of which was detected among school-age children hospitalized for community-acquired pneumonia.