Abstract： Objective To compare the outcomes of mononuelear stem (BMMNCs) and mesenchymal stem (MSCs) cell therapy for myoeardium infarction in rats. Methods In 45 female Lewis rats, myocardial infarction was induced by direct ligation of LAD. MSCS (2×106) and BMMNCs (2×106) harvested from male rats were injected directly into the infarcted myocardium in the infarct zone. Four weeks after therapy eehocardiography was performed and animals were sacrificed for further analysis. The survival outcomes of MSCs and BMMNCs were detected with expression of sry gene of Y chromosome by using fluorescence in situ hybridization (FISH). Results Four weeks later, left ventricular function was significantly improved in MSCs and BMMNCs groups compared with the control group (LVEF: 54.9±3.4%, 56.5 ±3.8% vs. 32.4:1±4.0%, P=O. O00). The thickness of LV anterior wall significantly increased in MSCs and BMMNCs groups compared with the control group (2.6±0.5 mm and 2.5±0.3 mm vs. 1.8±0.4 mm , P =0. 000). FISH showed that sry positive cells were observed in myocardium in MSCs and BMMNCs groups but not found in the control group. At the same time the number of sry positive cells in BMMNCs was significantly higher than that in MSCs (66.50 ±6.59 vs. 46.67 ±4.64, P =0.000). Conclusion The research shows that both MSCs and BMMNCs from bone marrow can repair the acute infarcted myocardium. The myocardial survival of BMMNCs is superior to that of MSCs.