The authors have studied the annual accounting documentation of the polyclinic component of the health care system of Moscow for the period from 1998 till 2017 with a view to elucidating the structure and dynamics of the incidence of acute sinusitis among the population of the megalopolis based on the information about medical aid appealability to policlinics. Simultaneously, the frequency of the application of various methods for the conservative treatment of this condition was evaluated. The total number of the patients suffering from acute sinusitis who visited the out-patient facilities and multi-disciplinary medical institutions of Moscow was estimated to be 660,758, with 64,531 patients having been hospitalized in various clinical centers during the study period (1.9% and 12.4% of the total number of the patients with ENT-pathology who applied for medical assistance and were hospitalized respectively). The number of patients presenting with acute bacterial sinusitis (ABS) diagnosed based at the out-patient facilities and multi-disciplinary medical institutions of Moscow increased by 1.9 times on the average during the last 5 years in comparison with the preceding 15 year period. The number of patients with the catarrhal form of acute bacterial sinusitis decreased by 23.2% within the same period whereas the number of patients with the purulent form of ABS increased by 56.6%. During the last 20 years, the frequency of prescription of such procedures as the puncture of maxillary sinus and the placement of the YAMiK-catheter has been showing the tendency toward decrease. To be precise, these procedures were prescribed in 39% and 34% cases to the patients with the purulent form of ABS respectively in 1998—2002 in comparison with 17% and 8% of the cases of acute bacterial sinusitis during the last 5 year period (2013—2017).