Abstract: AIM To observe the growth, differentiation and curative effect of autologus skeletal myoblasts (SM) following their transplantation into acute myocardial infarction(AMI) region by intracoronary infusion. METHODS Forty-five white Japanese big-ear rabbits were randomly divided into three groups: SM group, control group and sham operation group, with 15 animals were in each group. Gluteus were obtained for SM separation, purification and expansion in vitro. AMI model was obtained by ligating the coronary artery left anterior descending branch (LAD). 5×106 Bromodeoxy uridine(BrdU) labeled SM were infused into LAD after reperfusion. Equal serum-free medium alone was infused into control group after the ligation of the LAD. Except for the LAD ligation, sham operation group underwent the same procedures as control group. HE stain and anti-BrdU, anti-myosin-heavy chain(MHC, slow) immunohistochemistry stain were performed to evaluate the differentiation of the transplanted cells 4 weeks after transplantation. Left ventricle ejection fraction (LVEF) and shortening fraction (FS) were measured by echocardiography 24 hours and 4 weeks after transplantation. RESULTS Four weeks after transplantation, multinucleate muscle cells were seen in the MI region of the SM group by HE stain, and anti-BrdU and anti-MHC (slow) antibody immunohistochemistry showed positive. Twenty-four hours after transplantation, the LVEF and FS of animals in the sham operation group were better than those in SM and control group (P<0.01). Four weeks after transplantation, the LVEF and FS of animals in SM group and sham operation group were better than those in control group (P<0.01). CONCLUSION Autologus SM transplanted into AMI region by intracoronary infusion can survive in the AMI region, repairing the impaired myocardium and improving the cardiac function.