Obstructive sleep apnea syndrome (OSAS) is increasingly recognized in the pediatric population. It is characterized by a combination of partial upper airway obstruction and intermittent obstructive apnea that disrupts normal ventilation and sleep. It is estimated to occur in 1-3% of children with a peak age of 2 to 5 years. Common symptoms include habitual snoring, difficulty breathing during sleep, restlessness, and witnessed apnea. Adenotonsillar hypertrophy is the most common associated condition in otherwise normal children, but cranialfacial abnormalities, neuromuscular diseases, and obesity are also predisposing factors. Severe OSAS can have serious neurobehavioral and cardiorespiratory consequences including excessive daytime sleepiness, growth failure, school failure, behavioral problems, cor pulmonale, or even death. Diagnosis is based on data from the history, physical exam, and laboratory studies that confirm the presence and severity of the upper airway obstruction. Polysomnography has been the diagnostic tool of choice. Treatment depends on the severity of symptoms and the underlying anatomic and physiologic abnormalities. Since childhood OSAS is usually associated with adenotonsillar hypertrophy, the majority of cases are amenable to surgical treatment. However, there is increasing pediatric experience with CPAP therapy when tonsillectomy and adenoidectomy are either unsuccessful or inappropriate.