Objective: To investigate the effects of bone marrow-derived mononuclear cells (BMC) transplantation for the therapy of myocardial infarction (MI) in rabbits. Methods: 20 rabbits were randomly divided into 2 groups. MI was induced by ligation of the left anterior descending artery.In transplantation group(T,n=10), BMC transplantation was performed on 5-7 days after MI . Bone marrow (3-5 ml) was obtained from iliac crest and labeled with bromodeoxyuridine (Brdu) for 24-48 hours, BMC were transplanted into infracted myocardium through intramyocardial injection. Control animals (C,n=10) didn′t receive any treatment after MI. Echocardiography was performed for evaluating the cardiac function in 1 week and 5 weeks after MI. Hemodynamic and histological studies were performed in the 5 th weeks after MI. Results: LV ejection fraction of group T had no change, but group C decreased in the 1st week and 5th weeks after MI. The results of Group T having higher LV max +dP/dt and max-dp/dt, lower LV end-diastolic pressure showed comparing with that of group C in the 5th weeks after MI. Histological studies revealed that there were Brdu positive cells in the infarcted area in group T, and the vascular density of group T in the infarcted area was significantly greater in comparision with group C. No regeneration of smooth muscle cell and cardiomyocyte were found in the infarcted area. Conclusion: Transplantation of BMC may avoid the deterioration of cardiac function through vasculogenesis in the infarcted area,but the efficacy in amelioration of cardiac function is limited.