Supraglottitis is a rapidly progressive, life-threatening airway emergency in pediatric patients typically caused by Haemophilus influenzae type B (HIB). With distribution of the first efficacious vaccine for HIB in April 1985, changing disease patterns have begun to emerge; however, certain characteristics have remarkably persisted. The authors reviewed 252 pediatric patients with acute supraglottitis spanning the prevaccination and postvaccination years 1980 to 1992 at three major regional pediatric hospitals in Massachusetts, Ohio, and California, as well as at two community hospitals in Massachusetts. Findings include a decline in disease prevalence in all geographic areas with demographic, etiologic, and management evolution all seen. Children who had been immunized yet developed supraglottitis have been examined as predictive of future trends.