We studied the prevalence of sleep-disordered breathing in patients with Marfan's syndrome after observing obstructive sleep apnea (OSA) in a patient with this condition. We studied 25 patients (12 men and 13 women with a mean age of 31.9 +/- 2.8 yr) who fulfilled the diagnostic criteria for Marfan's syndrome. Twenty-one of the patients were randomly recruited. We compared them with 12 age-, height-, and weight-matched control subjects. On history, 23 of 25 patients snored to some degree, and 21 of 25 had mild to moderate daytime hypersomnolence. Standard nocturnal polysomnography revealed that 16 of 25 (64%) patients had an apnea/hypopnea index (AHI) greater than 5, with a mean of 20 +/- 3, and a mean minimal oxyhemoglobin saturation of 86 +/- 2%. Only one control subject had an AHI > 5, and the mean AHI for the group was 2 +/- 1 (p = 0.0005). Apneas and hypopneas were obstructive in nature. We conclude that there is a high prevalence of sleep-disordered breathing in patients with Marfan's syndrome, and that therefore the symptoms and signs of OSA should be sought in all such patients.