Obstructive sleep apnea (OSA) is characterized by recurrent episodes of partial (hypopnea) or complete interruption (apnea) in breathing during sleep due to airway collapse in the oral or pharyngeal region. Prospective studies have established the adverse cardiovascular consequences of OSA, including an increased risk for developing hypertension, coronary artery disease, stroke, and heart failure. However, more studies are needed to better assess the impact of OSA, and possible benefit of treatment with continuous positive airway pressure (CPAP) on cardiovascular mortality. The leading pathophysiological mechanisms involved in the changes triggered by OSA include intermittent hypoxemia and re-oxygenation, arousals and changes in intrathoracic pressure. Hypertension is strongly related with activation of the sympathetic nervous system, stimulation of the renin-angiotensin-aldosterone system and endothelial dysfunction. OSA should be suspected in hypertensive individuals, particularly in patients with resistant hypertension. CPAP treatment reduces blood pressure, and its effects are more pronounced in patients with high baseline blood pressure and elevated treatment compliance. At present, no clear evidence supports CPAP treatment for primary or secondary cardiovascular disease prevention.