Endothelial progenitor cells (Epcs) are precursors of endothelial cells and are mainly derived from bone marrow, with only 0. 01% content in peripheral blood. When a blood vessel is injured or otherwise stimulated, Epcs can migrate to the site of stimulation through the blood circulation to form new blood vessels. Epcs also have a high differentiation potential and can differentiate into endothelial cells, smooth muscle cells, osteoblasts, or cardiomyocytes. Because Epcs can migrate to injured areas to form new blood vessels and have the potential to differentiate into many kinds of cells, they are often used as seed cells to repair damaged areas of blood vessels or differentiate into other cells to repair defects. However, Epcs are difficult to isolate and cultivate. Researchers have found factors related to enhancement of the biological characteristics of Epcs. This article reviews the factors related to the biological characteristics of Epcs.