Sleep-disordered breathing, particularly the obstructive sleep apnea syndrome, is common during childhood. Complications include neurocognitive deficits, growth failure, and pulmonary hypertension. Nevertheless, sleep-disordered breathing is often unrecognized in children. New syndromes, such as the upper airway resistance syndrome, have recently been described. Polysomnography is invaluable for the evaluation of sleep-disordered breathing. Advances in diagnosis and management can alleviate much of the morbidity previously associated with sleep-related respiratory disorders.