The OSA syndrome, described over 100 years ago, was rediscovered in 1966. It is a common disorder, especially among fat, middle-aged men. Stentorian snoring and diurnal somnolence are the cardinal manifestations and should always lead to an examination during sleep. That examination (polysomnography) can demonstrate the pathognomonic events--repetitive apneas occurring in sleep--which signal the failure of the sleeping brain to maintain the patency of the supraglottic airway. All evidence points to the problem being an abnormal pharyngeal airway, one which has a shape or size or compliance that allows inspiratory collapse as the normal loss of pharyngeal dilator muscle tone occurs with sleep. The apneas are asphyxic events terminated by arousals which fragment sleep continuity and lead to the daytime sleepiness. Because the snoring occurs during sleep, the arousals are unremembered, and the sleepiness can develop so gradually that the patient may forget what normal alertness is like. It is important to interview the patient's spouse or partner. Besides obesity and maleness, other risk factors for OSA are diseases that have an impact on the configuration or effective compliance of the pharyngeal passageway. Recent studies support the clinical intuition that sleep apnea is undesirable. Sleepiness leads to accidents. The hypoxemia occurring during apnea can lead to potentially fatal cardiac dysrhythmias. A number of reports suggest that snoring and sleep apnea are associated with an increased risk of stroke, myocardial ischemia, and infarction. Finally, there are now two papers showing a significantly decreased probability of 5-year survival in patients with symptomatic sleep apnea. The good news is that treatment with tracheostomy or NCPAP improves mortality rates to normal. Approximately 90 per cent of patients can tolerate a night's initial trial with CPAP. Long-term acceptance of CPAP has now been reviewed in a number of studies, and it appears to be about 65 to 70 per cent.