Acute supraglottitis is a serious, potentially fatal infection in both adults and children. Haemophilus influenzae type b (Hib) is the most common cause in children, even in this era of the Hib vaccine. Most cases of acute supraglottitis in adults are thought to be caused by other bacterial organisms, viral or combined viral-bacterial infections, and noninfectious etiologies. Early visualization of the larynx is essential, as is establishment of a secure airway in selected cases. Most cases will respond to intravenous antibiotic therapy and will not require an artificial airway. Admission to an area of high-intensity nursing is essential. Daily laryngoscopy is necessary to monitor response to treatment. Although the incidence of acute supraglottitis in children has decreased, isolated cases will be encountered and demand high vigilance.