Sleep disorders as a new disease entity continues to experience growth and greater definition. Obstructive sleep apnea syndrome is a disorder characterized by a wide range of severity of subjective symptoms including daytime hypersomnolence, headache, altered mention, and snoring. Objective measurement using polysomnography documents episodes of apnea and desaturation level that provides more important information. From June, 1991 to May, 1993, we performed polysomnography in 142 cases of sleep disorders. The results were follows : 1) Types of sleep apnea were as obstructive type 113 cases(79.5%), mixed type 26 cases(18.3%), and central type 3 cases(2.1%). 2) In obstructive type, Apnea index ranged from 5.6 to 81.6(mean 30.9±18.3). Mean apnea duration was 23.5±4.2 second. Lowest oxygen saturation ranged from 21% to 89%(mean 71.4±11.7%). 3) In central type, Apnea index ranged from 8.3 to 30.7(mean 19.3±5.6). Mean apnea duration was 17.7±3.2 second. Lowest oxygen saturation ranged from 67% to 88%(mean 72.5±5.1%). 4) In postoperative polysomnography result, Mean apnea index was 12.1±9.5. Mean lowest SaO₂ was 82.1±4.3%. 5) Success Rates were 73%(criteria for success : change in A.I>50%) and 63%(criteria for success : lowest SaO₂>80%). The polysomnography is essential for accurate diagnosis of obstructive sleep apnea patients and provides important objective informations such as type of apnea, apnea index, lowest arterial oxygen saturation, and criteria of successful operation.