The intent of the study is to: 1) determine the prevalence of symptoms of SDB in pre-adolescent Caucasian and Hispanic children; 2) compare the prevalence of objectively measured SDB in pre-adolescent Caucasian and Hispanic children; 3) determine whether there are physiologic and anatomic differences among pre-adolescent children who have SDB including obstructive sleep apnea and upper airway resistance syndrome (UARS) and those who do not during quiet wakefulness; and 4) determine the association between SDB and school performance, neuro-cognitive ability and daytime symptoms.