Obstructive sleep apnea is a serious sleep disorder where breathing stops and starts during sleep repeatedly. It most commonly affects middle-aged and older adults and overweight people. It occurs when throat muscles intermittently relax and block airway during sleep. Important sign is snoring. Breathing pauses can last from a few seconds to minutes. Normal breathing then starts again, often with a loud snort or choking sound. Sleep apnea usually is a chronic (ongoing) condition that disrupts sleep. It Rrsults in poor quality of sleep, making the person tired and fatigued during the day and excessive daytime sleepiness. If left untreated,sleep apnoea can be disastrous and a serious health hazard. It increase the risk of high blood pressure,stroke,obesity,diabetes, heart failure, irregular heartbeats, work-related or driving accidents. There are many investigations to evaluate obstructive sleep apnoea like estimation of blood sugar,ECG,Arterial blood gas,polysomnography. This desease equires long-term management. Lifestyle changes,as weight reduction,control of hypertension and Diabetes,mouthpieces, surgery, and breathing devices like CPAP/BIPAP can successfully treat it.