Obstructive sleep apnea (OSA) is a frequently underdiagnosed condition that has emerged as an increasing medical problem with important social and financial implications worldwide. Its prevalence may reach 25% in middle-aged men and 11% in women. The most important risk factor for OSA is obesity - every 10% weight gain increases the incidence of the disease 6 times. OSA usually occurs in middle age males and is characterized by history of snoring, daytime somnolence and nocturnal choking or gasping. The underlying cause is transient cessation of airflow due to occlusion of the oropharyngeal tract. Episodes of apnea are considered important if they persist for longer than 10 seconds, but in some cases they may last as long as 2 minutes. The airway occlusion results in recurrent hypoxia, hypercapnia, arousals from sleep, compensatory hyperventilation leading to secondary hypocapnia and generation of exaggerated negative intrathoracic pressure that all can either directly or indirectly be harmful to the cardiovascular system through several pathways like sympathetic activation, inflammation, oxidative stress and endothelial dysfunction. Recurrent episodes of apnea/hypoxia may negatively affect the function of many organs, e.g. they induce (cyclical bradycardia during the apneic episodes, followed by tachycardia during the ensuing ventilatory phases) or rise blood pressure. Moreover, OSA is a well established risk factor for systemic hypertension myocardial infarction or stroke and it has been documented that blood pressure rises in a very consistent fashion during apneic episodes. The mechanisms responsible for this phenomenon are complex because the direct effects of apnea (hypoxemia and low intrathoracic pressure) are modified by cardiopulmonary reflexes. Undoubtedly, the rapid increase in arterial pressure that occurs at the end of an apneic episode is mainly mediated by surges in sympathetic function during the arousal reaction.