The data on magnesium supplementation in patients with acute myocardial infarction (AMI) is conflicting. Although a number of relatively small randomized clinical trials have demonstrated a remarkable reduction in mortality when administered to relatively high risk AMI patients, two recently published large-scale randomized clinical trials (the Fourth International Study of Infarct Survival and Magnesium in Coronaries) failed to show any superiority of intravenous magnesium over placebo. Nevertheless, the theoretical potential benefits of magnesium supplementation as a cardioprotective agent in coronary artery disease (CAD) patients, in conjunction with previous promising results from work in animal and humans, its relatively low cost, easy administration, with no need for special expertise, and relatively free of adverse effects, gives magnesium a place in treating CAD patients, especially high-risk groups such as CAD patients with heart failure, the elderly and hospitalized patients with hypomagnesemia.