Acute epiglottitis, which is almost exclusively caused by Haemophilus influenzae type b, was studied retrospectively in children 0 to 15 years old in a defined region of southwest Sweden from 1971 through 1980; 211 patients with clinically well-documented acute epiglottitis were found. The age-specific incidence was 14/100,000/year, which was higher than the incidence of H. influenzae meningitis. The median age was 4 years. Because 96% of the patients were older than 18 months, disease in those patients could theoretically have been prevented by the purified H. influenzae polysaccharide vaccine. Only a few patients had underlying diseases. In 186 patients an artificial airway was established. Even though all patients survived without sequelae, the large incidence of the disease emphasizes the importance of H. influenzae in older children.