Many snoring children may have primary snoring (PS) defined as habitual snoring without alteration in sleep architecture, alveolar ventilation and oxygenation. On the other hand, obstructive sleep apnea (OSA) is a condition characterized by recurrent episodes of gas exchange abnormalities and repeated arousals that affects up to 2-3% of all 2-8 year-old children, with African-American (3-fold) and obese children (6-10 fold) being at much increased risk. Thus far, overnight polysomnographic assessment (PSG) is required for the definitive diagnosis of OSA in children, since clinical history and physical examination are insufficient to confirm its presence or severity and most of the abbreviated tests have also limited value as a screening method. Unfortunately, overnight sleep studies are onerous, labor-intensive, impose substantial discomfort on the children and their families, and are relatively inaccessible to children, such that waiting times between referral for evaluation to diagnosis commonly take 5-6 months across the USA. Furthermore, access for such sleep studies among underserved and inner city children is even less likely to be available, particularly considering that less than 150 physicians across the USA are currently trained and certified to evaluate sleep disorders in children. Considering that complete reversal of the SDB-associated morbidities is possible following effective treatment (e.g., improvements in learning and behavior), it is therefore rational to identify these children as soon as possible using simple and reliable diagnostic procedures. A feasible, yet challenging approach would be the development of simple and rapid screening tests using either blood or urine that would enable identification of children with OSA for subsequent clinical workup and treatment. We propose to develop such a system under this SBIR project.