The purpose of this study is to determine whether sleep endoscopy performed in high-risk pediatric patients with obstructive sleep apnea (OSA) at the time of adenotonsillectomy (AT) can predict whether the AT will be successful as an initial treatment for OSA. We hypothesize that patients with multiple sites of obstruction in addition to adenotonsillar hypertrophy (e.g. the nasal airway, velum, base of tongue, supraglottis) will be more likely to have residual sleep apnea on postoperative sleep testing.