Obstructive sleep apnea hypopnea syndrome (OSAHS) is a common sleep disorder in adults that is increasingly recognized in children, affecting 1 to 3% of children. Children experience a spectrum of severity related to the degree of upper airway obstruction, the duration of the disease, and the presence or absence of hypoxemic episodes. Failure to diagnose and treat OSAHS can result in serious, but generally reversible consequences for the child including impaired growth, neurocognitive and behavioral dysfunction, and cardiorespiratory failure. Even mild OSAHS appears linked to reversible health consequences. Adenotonsillar hypertrophy is the major predisposing factor for OSAHS in childhood. However, enlarged tonsils and adenoids can be a normal finding in young children and are not diagnostic for OSAHS. The identification of children with OSAHS is often difficult because affected children may have no signs or symptoms when awake. Furthermore, clinical assessment cannot reliably distinguish between simple snoring and OSAHS. Adenotonsillectomy is the most common therapy for OSAHS in children, but surprisingly, only a small percentage of children undergo any diagnostic testing prior to surgery. Thus, the challenge is to develop new diagnostic strategies that effectively screen, identify, and treat children most likely to benefit from specific treatment.