Obstructive sleep apnea (OSA) is common in general population. There is an accumulating research evidence for an independent relationship between OSA and cardiovascular morbidity and mortality. This relationship is stronger in clinical cohorts compared with the general population, which suggests that concomitant OSA in subjects with traditionally recognized risk factors such as obesity, hypertension, smoking, and hyperlipidemia may provide an additive risk factor for the cardiovascular consequences. In the current article, the clinic-and population-based epidemiologic data will be reviewed in this context.