Vitamin D deficiency is a condition that affects a high percentage of individuals of all ages. Considerable attention has been paid recently to the possible role of deficiency of this vitamin in the development of several chronic diseases, including cardiovascular and metabolic diseases. In particular, vitamin D deficiency is associated with an increase in conditions such as obesity, insulin-resistance, hypertension, diabetes, and an increased risk of death from these pathologies. There is also a significant correlation with mortality for major cardiovascular events such as heart failure, myocardial infarction, sudden cardiac death, stroke, atrial fibrillation, and peripheral vascular disease. The pathophysiological mechanisms of these correlations are yet to be determined, but hyperactivity of the renin-angiotensin-aldosterone system seems to play a leading role. The role of therapy with vitamin D supplements in improving cardiovascular outcome in patients with low levels of vitamin D remains to be determined.