Any patient presenting with daytime sleepiness, snoring, frequent arousals, and observed apneas warrants evaluation for OSA. A more extensive evaluation is necessary when evidence of hypoventilation exists, whether this is frank hypoxemia or only an elevation in the serum bicarbonate level. CPAP ameliorates OSA, but patients do not always tolerate it well, and weight loss remains the simplest and best therapy. Unfortunately, weight loss is notoriously difficult for patients to achieve, and the next challenge is to increase our knowledge of the physiology of weight loss.