Adenotonsillar hypertrophy has been documented to cause chronic upper airway obstruction resulting in cardiopulmonary sequelae in children. It has been less recognized that long-term adenotonsillar hypertrophy may additionally cause acute, life-threatening airway obstruction. A review of 5000 adenotonsillectomies performed at 3 New York Medical College affiliated hospitals from 1982 to 1989 showed 6 pediatric patients with progressive upper airway obstruction severe enough to necessitate intubation in the emergency room or operating room, and subsequent urgent adenotonsillectomy after cardiorespiratory stabilization. Patients were monitored in the ICU with pre- and postoperative blood gases. Observations of cyanosis, cor pulmonale, and use of accessory respiratory muscles were carefully recorded. This study illustrates that life-threatening upper airway obstruction may be due to chronic adenotonsillar enlargement and require treatment by urgent adenotonsillectomy.