Improved case identification of children with upper airway obstruction during sleep should result if physicians are aware of such signs and symptoms as excessive daytime sleepiness, loud snoring, restless sleep, recurrent nocturnal enuresis, systemic and pulmonary hypertension, undergrowth or obesity, and cor pulmonale. Furthermore, partial airway obstruction during wakefulness may be a risk factor for the development of sleep apneas or hypopneas. In suspected cases, polysomnography is a useful method for confirming and quantitating the type (central, obstructive, or mixed) and extent of ventilatory disturbance during sleep and its functional significance (such as arterial oxyhemoglobin desaturation or cardiac arrhythmia). Other methods may be employed to yield similar data. There seem to be at least two groups of children reported in the literature, those in whom there is a specific surgically correctable lesion (such as adenotonsillar hypertrophy) versus those who eventually need tracheotomy because of collapse of upper airway musculature during sleep. In the latter group of children, it is necessary to hypothesize an additional defect in the CNS regulation of respiration during sleep. Further research is necessary to define the boundary between normal and abnormal breathing during sleep, and to understand more thoroughly the effects of intermittent hypoventilation on daytime functioning.