목적: There have been many changes in the incidence, diagnosis and treatment of otologic diseases worldwide. There are various factors which affect the incidence rate of disease involving environmental and social factors. We aimed to analyze the clinical trend regarding the incidence of otologic diseases in Asan Medical Center, the biggest tertiary referral center in South Korea, over the past 20 years involving the coronavirus disease-2019 (COVID-19) pandemic period (from December 2019 to May 2023). 방법:We retrospectively reviewed the number of patients newly diagnosed as sudden sensorineural hearing loss (SSNHL) or Bell’s palsy at outpatient clinic and patients who underwent ventilation tube insertion due to persistent otitis media with effusion (OME), preauricular fistulectomy due to recurrent infection of preauricular fistula, or tympanomastoidectomy due to chronic otitis media (COM) from January 2004 to December 2023 in Asan Medical Center. We analyzed overall trends (increase or decrease) of otologic diseases and also looked into COVID- 19 pandemic period under social isolation. 결과:Patients newly diagnosed as SSNHL increased over 20 years and there was a rapid increase of SSNHL patients after outbreak of COVID-19 pandemic (667 patients in 2019, 676 patients in 2020, 928 patients in 2021, 1176 patients in 2022, and 1233 patients in 2023). Regarding ventilation tube insertion, the incidence of OME showed a tendency to decrease following the COVID-19 outbreak but recovered in 2023, the year of declaring end to COVID-19 pandemic (611 patients in 2019, 400 patients in 2020, 354 patients in 2021, 376 patients in 2022, and 546 patients in 2023). Tympanopmastoidectomy due to COM showed a tendency to keep decreasing in 2010-2020s than 2000s. There were no noticeable changes in the incidence of Bell’s palsy and number of patients who underwent preauricular fistulectomy involving the pandemic period. 결론:When we analyzed the clinical trend of the incidence of otologic diseases in a single institution over time, there was a noticeable decrease in OME and significant increase in SSNHL during the COVID-19 period. COM which required tympanomastoidectomy kept decreasing gradually. The effects of social changes (lockdown, continuous use of facial masks, social distancing, and reduction of social activities) seem to affect decrease in incidence of OME by reducing chances of other bacterial/viral infection and immunity gain. Although pathophysiology is unknown and causative link lacks, COVID-19 may be a potential related factor regarding rapid increase of SSNHL in 2020s.