Background: Recent evidences suggest that bone marrow-origin stem cells can improve cardiac function in patients with myocardial infarction. We aimed to assess the safety and efficacy of intracoronary infusion of mobilized peripheral blood stem cells in patients with large myocardial infarction and subsequent left ventricular dysfunction, in whom the stem cell therapy might show maximal benefit. Methods: To reduce potential bias of image analysis, we enrolled acute myocardial infarction patients with proximal left anterior descending artery occlusion. After successful percutaneous coronary intervention, 10 patients were received intracoronary infusion of autologous peripheral blood stem cells mobilized by granulocyte-colony stimulating factor (G-CSF). After 6 months, changes in left ventricular systolic function, perfusion, and viability were assessed by echocardiography, SPECT, MRI, and PET. Results and Conclusion: Up to now, 5 patients completed 6 month follow-up. Global left ventricular ejection fraction (LVEF) measured by MRI was 36.6+-12.2% at baseline. At this point of time, cell transplantation did not increase the risk of adverse clinical events or proarrhythmic effects, but one significant in-stent restenosis was identified. Further data will be presented at the meeting.