The purpose of this study is to determine whether sleep endoscopy can predict whether their AT will be successful as a treatment for OSA. Our hypothesis is that subjects with multiple areas of obstruction in addition to large tonsils will be more likely to have residual OSA after AT. Sleep endoscopy is a procedure performed during drug-induced sleep that involves passing a flexible endoscope through the subject's nose into the back of the throat to look for sources of obstruction while breathing spontaneously.