Obstructive sleep apnea (OSA) is the most common form of sleep-disordered breathing and frequently coexists with obesity. Almost 15 million Americans are affected by this disorder. This prevalence is likely increasing, given the current epidemic of obesity. Recent data confirm an association between sleep apnea and several cardiovascular disease conditions, suggesting that OSA may be a new risk factor for coronary artery disease, heart failure, heart rhythm disturbances and hypertension, independent of body mass index. In this review, the authors focus on the nature of the association between OSA and hypertension, the evidence suggesting a causal interaction, and discuss the potential pathophysiologic mechanisms responsible. These mechanisms include activation of the sympathetic and renin-angiotensin-aldosterone systems (RAAS), oxidative stress, and systemic and vascular inflammation, all of which could link OSA to a sustained increase in blood pressure. The authors also review potential therapeutic strategies for the hypertensive patient with OSA.