Recent studies indicate that deficient vitamin D status may increase risk of both ischemic and nonischemic cardiovascular diseases independently of established cardiovascular risk factors. The role of vitamin D in potentially regulating many functions in the cardiovascular system is just beginning to be understood. Among the potentially relevant mechanisms for cardiovascular diseases, vitamin D may influence blood pressure through the renin-angiotensin system, parathyroid hormone levels, myocardial function, inflammation, and vascular calcification. Cardiovascular risk appears especially elevated at 25-hydroxy-vitamin D levels below 10 or 15 ng/mL, and optimal levels may be at least 30 ng/mL. Among individuals who are not receiving substantial exposure to sun, intakes of 1000 to 2000 IU may be needed to achieve levels of at least 30 ng/mL. Further study, including properly designed randomized control trials, is required to further establish the role of vitamin D on cardiovascular diseases.