Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common disorder in middle-aged populations. It causes excessive daytime sleepiness, mood irritability and neurocognitive impairment which affects patient’s quality of life and increases their risk of motor vehicle accidents, cardiovascular morbidity and mortality. This article presents the most recent information of OSAHS including pathophysiology, clinical symptoms and signs, airway evaluation, sleep studies and its indications, diagnosis and choices of treatment.