Granulocyte colony stimulating factor (G-CSF) is a pleiotropic cytokine. It is produced mainly by monocytes and macrophages upon activation by endotoxin, TNF-alpha and IFN-gamma. Human G-CSF is 73% identical at the amino acid level to mouse G-CSF and the two proteins show species cross-reactivity. G-CSF receptor was expressed on cardiomyocytes and G-CSF activated the Jak/Stat pathway in cardiomyocytes. The G-CSF treatment did not affect initial infarct size at 3 d but improved cardiac function as early as 1 week after myocardial infarction. And the G-CSF induces stem cell mobilization by decreasing bone marrow SDF-1 and up-regulating CXCR4.