OBJECTIVE To characterize the clinical features of acute epiglottitis in adults and to identify factors associated with airway intervention. METHODS Case series. METHODS Northern California health maintenance organization. METHODS A total of 129 patients aged 18 years or older with laryngoscopically confirmed acute epiglottitis admitted from November 1986 through October 1991. RESULTS The mean patient age was 47 years (range, 18 to 85 years) and the male-to-female ratio was 1.8 to 1.0 (P < .001). The most common symptoms were sore throat (95%) and odynophagia (94%); the most common signs were muffled voice and evidence of pharyngitis. Nineteen patients (15%) received airway intervention, including seven with tracheotomy and 12 with endotracheal intubation. The remaining 110 patients recovered fully without airway intervention. In multivariate analysis, factors associated with airway intervention were stridor (relative risk [RR], 6.2; 95% confidence interval [CI], 1.7 to 22.9) and sitting erect (RR, 4.8; 95% CI, 1.3 to 16.1). Six (12%) of 52 blood cultures yielded Haemophilus influenzae type b. Major complications occurred in six patients (5%), but no deaths occurred. CONCLUSIONS Most adults who have acute epiglottitis can be managed conservatively and have low morbidity and mortality.