OBJECTIVE To review randomized control clinical trial (RCT) literature and prospective studies for the safety and efficacy of magnesium supplements in patients with coronary heart disease (CHD) or with CHD risk. METHODS Databases were searched using the keywords: magnesium, heart disease, endothelium, prevention, treatment, therapy, level, and supplement. CONCLUSIONS There were no reports of adverse effects from magnesium supplementation in any of the studies. Subjects reporting lower dietary magnesium intake had significantly lower serum magnesium concentrations than those reporting higher dietary magnesium intake and, in some cases, had a significantly higher frequency of supraventricular beats. There was a modest relationship between dietary magnesium intake and a reduced risk of CHD in male subjects; however, there was no noted decrease in the development of CHD disease in women who had high magnesium intake. CONCLUSIONS Magnesium is vital for many functions in the body and magnesium supplementation is safe. There is a possible association between a modestly lower risk of CHD in men and increased magnesium intake; therefore, it is reasonable to encourage diets high in magnesium as a potential means to lower the risk of CHD.