Khayat RN, et al. - The role of renin-angiotensin system (RAS) in the obstructive sleep apnea (OSA) induced vascular endothelial dysfunction (VED) is not well understood. In this current study, an association was shown between VED and upreguation of angiotensin receptors type-1 (AT-1) expression, which was reversible with continuous positive airway pressure (CPAP), in OSA patients with no to minimal cardiovascular disease (CVD) risk. Additionally, it was observed that endothelial oxidative stress was reversible with AT-1 blockade (ARB). Overall, RAS activation may play a vital role in the development of early CVD risk in OSA patients.