Hypertension and atherosclerosis are well-known precursors of ischemic heart disease, stroke and sudden cardiac death. Although there is general agreement that the atheroma is the hallmark of atherosclerosis and is found in coronary obstruction, there is no agreement as to its etiology. It is now becoming clear that a lower than normal dietary intake of Mg can be a strong risk factor for hypertension, cardiac arrhythmias, ischemic heart disease, atherogenesis and sudden cardiac death. Deficits in serum Mg appear often to be associated with arrhythmias, coronary vasospasm and high blood pressure. Experimental animal studies suggest interrelationships between atherogenesis, hypertension (both systemic and pulmonary) and ischemic heart disease. Evidence is accumulating for a role of Mg2+ in the modulation of serum lipids and lipid uptake in macrophages, smooth muscle cells and the arterial wall. Shortfalls in the dietary intake of Mg clearly exist in Western World populations, and men over the age of 65 years, who are at greatest risk for development and death from ischemic heart disease, have the greatest shortfalls in dietary Mg. It is becoming clear that Mg exerts multiple cellular and molecular effects on cardiac and vascular smooth muscle cells which explain its protective actions.