Environmental exposure is an important but underappreciated risk factor contributing to the development and severity of cardiovascular disease (CVD). The heart and vascular system are highly vulnerable to a number of environmental agents--ambient air pollution and the metals arsenic, cadmium, and lead are widespread and the most-extensively studied. Like traditional risk factors, such as smoking and diabetes mellitus, these exposures advance disease and mortality via augmentation or initiation of pathophysiological processes associated with CVD, including blood-pressure control, carbohydrate and lipid metabolism, vascular function, and atherogenesis. Although residence in highly polluted areas is associated with high levels of cardiovascular risk, adverse effects on cardiovascular health also occur at exposure levels below current regulatory standards. Considering the widespread prevalence of exposure, even modest contributions to CVD risk can have a substantial effect on population health. Evidence-based clinical and public-health strategies aimed at reducing environmental exposures from current levels could substantially lower the burden of CVD-related death and disability worldwide.