Acute myocardial infarction (MI) leads to myocardial necrosis and is, by nature, an irreversible injury. The major goal to reverse left ventricular remodeling would be the enhancement of regeneration of cardiac myocytes as well as the stimulation of neovascularization within the infarct area, by repopulation of the injured myocardium with healthy autologous cells. In March 2001, the first patient was treated with direct intracoronary administration of autologous mononuclear bone marrow cells after acute MI. As improvements in myocardial function and perfusion could be detected 3 months later without any complications - a study was initiated in Düsseldorf. Until now 40 patients have been investigated. After a three month follow-up period, significant improvements concerning myocardial function, perfusion and metabolism could be obtained. This therapeutical effect may be attributed to bone marrow cell-associated myocardial regeneration and neovascularization. These results demonstrate that functional and metabolic regeneration of infarcted myocardium can be safely realized in humans by bone marrow mononuclear cell transplantation.