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 pharyngeal region. OSA and its cardiovascular consequences have been widely explored in observational and prospective studies. Most evidence verifies the positive relationship between OSA and hypertension, coronary artery disease, atrial fibrillation, 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 dyslipidemia, type 2 diabetes, insulin resistance and 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 impairment of endothelial function. The high prevalence of OSA in the general population, hypertensive patients and especially obese individuals and patients resistant to antihypertensive therapy, highlights the need for effective screening, diagnosis and treatment of OSA to decrease cardiovascular risk.