Obstructive sleep apnea (OSA) is strongly associated with hypertension. The seventh report of the joint national committee (JNC-VII) guidelines have placed OSA at the top of the list to induce secondary hypertension. Severe OSA patients revealed the high prevalence of hypertension. Compared with normal subjects, patients with OSA had a higher 24-hour blood pressure, especially nighttime blood pressure. More recently, prospective data showed that sleep apnea syndrome was an independent risk for onset of hypertension. There is a lot of evidence that demonstrates that treating OSA using continuous positive airway pressure (CPAP) is an effective for management of OSA.