Obstructive sleep apnea (OSA) is the intermittent cessation of breathing during sleep due to the collapse of the pharyngeal airway. Obstructive sleep apnea is a complex disease whose etiology is multifactorial and because the final common pathway for this disease, whether caused by neurologic, muscular, anatomic, or other etiology, is obstruction of the upper airway during nocturnal respiration, The identification of the sites of upper airway obstruction in patients with obstructive sleep apnea is the cornerstone in choosing the appropriate surgical intervention. Identification of the sites of UA occlusion during sleep has been attempted by a variety of techniques including, upper airway measurements, endoscopy, radiology, and physical examination. The aim of this study is to analyze and compare between each of the above-mentioned techniques as regards advantages and disadvantages in detection of the level of obstruction in obstructive sleep apnea patients.