Fifty-five cases of acute epiglottitis were diagnosed and treated at the Children's Hospital of Philadelphia between 1985 and 1991. To evaluate the changing patterns of the disease over recent years, we compared the current results with those obtained from an earlier study reported at our institution in 1979. The overall annual incidence was higher in recent years than in the earlier study, with a sharp decline in new cases over the last two years. Thirty-six percent of the Hemophilus influenzae type B (HIB) infections were ampicillin-resistant in recent years, while no resistance had been found in the past. Twenty-seven percent of the cases were vaccine failures, all before 1990. Endotracheal intubation was the sole method for upper airway maintenance, while in the past 31% of the children underwent a tracheotomy. No mortality or long-term complications were found in either study.