Critical limb ischemia (CLI) results from severe occlusive disease that impairs distal limb perfusion to the point where oxygen delivery is no longer adequate to meet the metabolic needs of the tissue, even under resting conditions. The limits of peripheral artery disease (PAD) compensatory mechanisms, such as distal vasodilatation and collateral formation, have been exceeded at this point. PAD is a widespread disease, affecting up to 15% of all adults older than 55 years. Formation of true new blood vessels, or angiogenesis, and development of collateral vessels from preexisting blood vessels, or arteriogenesis, is important in the pathophysiology of vascular disease. By stimulating these processes we might be able to provide an alternative treatment strategy for patients with lower limb ischemia. In response to tissue injury and remodeling, neovascularization usually occurs via the proliferation and migration of progenitor endothelial cells (EPC) from preexisting vasculature. The EPCs resident within bone marrow and peripheral blood, so it seems implantation of BM cells can contribute to injury-induced and pathology induced neovascularization. Indeed, recent studies have shown that bone-marrow mononuclear cell (BM-MNC) implantation increases collateral vessel formation in both ischemic limb models and patients with limb ischemia. In addition, granulocyte-colony stimulation factor could mobilize the EPCs to peripheral blood. After BM-MNC implantation, G-CSF can contribute more EPC in PB for effective angiogenesis in PAD patients.