Role of vascular endothelial growth factor in the response to vessel injury. In the post-embryonic life, physiological angiogenesis is tightly controlled. Angiogenesis also occurs in pathological circumstances such as tumor vessel proliferation, retinal neovascularization and ischemia. The development of collateral circulation is not only not deleterious, but life saving. Other cases such as neoplastic neovascularization are the basis of the continuous growth of tumors and metastases, and therefore constitute a target of therapeutical efforts. Among a list of molecules able to control angiogenesis, we emphasize the pivotal role of vascular endothelial growth factor (VEGF). VEGF is a potent mitogen for endothelial cells, but is devoid of mitogenic activity for other cell types. VEGF is a polypeptide with four main different isoforms that are remarkably different in terms of solubility and affinity for matrix proteins. VEGF interacts with two endothelial cell-specific tyrosine kinase receptors. The main interest of its study lies in VEGF’s role in pathological angiogenic processes, where an increase in the VEGF mRNA expression has been consistently observed. An interesting example is the up-regulation of VEGF’s and VEGF receptors’ mRNA in a considerable number of human tumors and retina, where they have a critical role in the development of neovascularization. In recent work in our laboratory, we have found further potential interactions of VEGF with pathophysiological mechanisms, namely, the increase in VEGF gene expression under exposure to reactive oxygen species and the positive interaction between VEGF and erythropoietin. VEGF has outstanding possibilities for therapeutic applications aimed at inhibiting or favoring the development of new vessels.