The study is part of an initiative, Obstructive Sleep Apnea in Children, which was released in December, 1997 with co-sponsorship from the National Institute of Dental and Craniofacial Research and the National Institute of Child Health and Human Development. The goal of the initiative is to define abnormalities in airway structure and function responsible for obstructive sleep apnea in children, ages 3 to 12, and to identify physiological and clinical measures associated with increased morbidity.