Studies in hypertensive populations to date suggest that nondipping during the night, heightened blood pressure variability during the night, and nocturnal hypertension all predict future risk for cardiovascular morbidity and mortality, and are better prognostic factors than daytime hypertension. This chapter discusses the effects of sleep apnea treatment on hypertension. Although the prevalence of obstructive sleep apnea (OSA) increases with age, younger patients with OSA may be more prone to having cardiovascular consequences, including hypertension. Several studies suggest that the association between OSA and hypertension is more robust in the non-elderly. Different screening questionnaires have been developed and tested in attempts to identify patients at high risk for OSA. More studies are necessary to further elucidate pathogenetic mechanisms by which OSA causes hypertension and to determine the magnitude of the effect of OSA and its treatments on blood pressure.