Over the past 25 years, there has been an increased understanding of pediatric obstructive sleep apnea (OSA). The initial descriptions of children presenting with cor pulmonale and other serious physiological consequences of OSA have been augmented by descriptions of the effects of OSA on more subtle outcomes such as cognitive abilities and behavior. We now understand that OSA in children is associated with more than simple upper airway obstruction but includes abnormalities in upper airway function. OSA also has adverse effects on the physiology of the child such as alterations in glucose metabolism and inflammation that have recently come to light. A number of these processes are reversible with intervention, and we have a better understanding of the outcomes of various interventions as well as what is a normal sleep pattern in children.