The role of magnesium in coronary artery disease has been evaluated extensively during the last three decades. The intravenous application of magnesium in acute myocardial infarction is of major importance, the beneficial effects have been underlined in several studies. Magnesium is of significance in the pathomechanisms of reperfusion injury and reduction of malign arrhythmias in the critical acute phase of myocardial infarction, if applied intravenously. However, the promising results of LIMIT-2 could not be confirmed by the data of ISIS-4. The timing of magnesium therapy is probably the most important key factor. Similar to the guidelines of thrombolytic intervention, magnesium has to be administered as early as possible, at the latest before myocardial reperfusion has started. Nevertheless, because of conflicting results of prior trials doubts on the efficacy of intravenous magnesium in myocardial infarction still remain. The multinational, multicenter trial MAGIC has been set up to evaluate the optimal patient cohort as well as the ideal dose regimen for the application of intravenous magnesium sulphate in patients with acute myocardial infarction. The answer on the open questions on intravenous magnesium sulphate in myocardial infarction could be "MAGIC".