The sleep apnea syndromes have been recognized clinically in the United States only within the past ten years. The true extent of the problem is not known, but it seems certain that these syndromes are much more common than was generally assumed five years ago. Every clinician should be aware of the signs and symptoms of sleep apnea because of the rapid and prompt response to therapeutic measures. Sleep apnea syndromes, whether obstructive or central, can result in systemic or pulmonary hypertension, arterial blood gas abnormalities, life-threatening cardiac arrhythmias, chronic respiratory failure, sleep disturbances, narcolepsy, excessive daytime somnolence, sexual dysfunction, and the suspicion of mental retardation. The immediate and dramatic improvement produced by tracheostomy in the obstructive type of sleep apnea, or nocturnal ventilatory support in the central type, can not only enhance the quality of life for these patients, but return them to functional and productive lives.