Sleep-disordered breathing (SDB) is increasingly recognized as an important clinical problem in children; however, the clinical, anatomic, and physiologic correlates of SDB have not been studied extensively in a general population sample using polysomnography to document the presence of SDB. The Tucson Children’s Assessment of Sleep Apnea Study is a longitudinal cohort study of 503 Caucasian and Hispanic children aged 6 to 12 years old who underwent polysomnography and neurocognitive testing at the time of recruitment. Subsets of the cohort had additional MR imaging and pulmonary physiologic testing. Initial cross-sectional analyses indicate that SDB is associated with behavioral abnormalities, hypertension, learning problems, and clinical symptoms such as snoring and excessive daytime sleepiness. Future follow-up of the cohort will assess the impact of SDB on subsequent childhood development.