It has recently been demonstrated that postnatal neovascularization is not restricted to angiogenesis, but also includes vasculogenesis. During adult vasculogenesis, bone marrow (BM)-derived endothelial progenitor cells (EPCs) are recruited to the systemic circulation in response to certain cytokines and/or tissue ischemia, and incorporate into sites of neovascularization. EPCs have also been investigated as therapeutic agents in a 'supply-side' approach to promoting neovascularization under pathological conditions. This review highlights the discovery of BM-derived EPCs and their therapeutic potential for vascular regeneration.