Oxidative stress is associated with development and progression of cardiovascular disease. Angiotensin II produces oxidative stress and endothelial dysfunction, and its actions may be attenuated by the activity of angiotensin converting enzyme type 2 (ACE2) which converts angiotensin II to the vasoprotective peptide angiotensin (1-7). Similarly, increased oxidative stress is associated with aortic valve stenosis in humans and mice. In my thesis studies, I explore mechanisms of modulation and generation of oxidative stress in cerebral arteries and heart valves. First, I tested the hypothesis that ACE2 deficiency increases oxidative stress and vasomotor dysfunction in cerebral arteries, and examined the role of ACE2 in vascular aging. Vasomotor function was assessed in the basilar artery ex vivo of adult and old