We reviewed acute epiglottitis (AE) and identified factors associated with airway intervention. This report was a retrospective review of patients with AE and compared with factors associated with airway intervention. We reviewed 96 patients who were diagnosed with AE in our hospitals in Japan. Ninety-two (96 per cent) patients were adults, and no seasonal variation in the incidence of AE was encountered. Eight (8 per cent) patients had tracheostomy and endotracheal intubation had not been done. We found that symptoms of stridor and muffled voice, a rapid clinical course, and diabetes mellitus were the factors associated with airway intervention. Extremely severe swelling of the epiglottis such that only less than half of the posterior vocal fold (scope classification (SC): III) could be seen, and extension of the swelling to the arytenoids (SC: B) were the two factors that were strongly associated with airway intervention.