More women die from complications related to cardiovascular disease (CVD) each year than men, yet dysfunction of the heart and blood vessels is still often considered to be primarily a “male” health issue. Emerging data indicate that oxidative stress is an important etiological factor for CVD in women, and it is apparent that female hormones, like estrogen, exert powerful influences on oxidative balance. This chapter will present recent findings and current concepts concerning oxidative stress and cardiovascular function in women. Prominent sources of oxidants in the heart and vasculature will be discussed (e.g., NADPH oxidase, xanthine oxidase (XO) , mitochondria, and uncoupled NOS), as well as the effect of estrogen on activity and expression of these proteins in the context of normal hormonal levels and exogenous estrogen replacement therapy. We will also discuss three prominent CVDs that exhibit a rather marked—and at times, surprising—sexual dimorphism in their epidemiology, and consider the ability of estrogen to influence the development and progression of these pathophysiological states in terms of cellular/molecular mechanisms. The overall goal of the chapter is to provide the reader with a rather comprehensive overview of how oxidative stress impacts women’s cardiovascular health, and to review the potential role of estrogen as both a preventive and causative factor in CVD among women.