The obstructive sleep apnea syndrome (OSAS) is a common cause of morbidity in childhood. Arousal from sleep during airway obstruction has been regarded as a protective reflex that reestablishes airway patency and prevents severe, life-threatening asphyxia. However, children, in contrast to adults, often do not have cortical arousals in association with apneas. It is still not clear whether this lack of arousal in children is due to a general defect in arousal mechanism or to more specific defects. We have previously shown that children with OSAS have impaired arousal responses to hypercapnia and inspiratory resistance loading. However, this may have developed secondary to OSAS. The objective of this study is to analyze whether the overall arousal threshold is abnormal, by evaluating the arousal response to an acoustic stimulus. To date, we have evaluated acoustic arousal in five subjects with OSAS and two controls. Further subjects need to be studied before the data can be analyzed.