Angiotensinogen (AGT), also known as SerpinA8, is a member of the serpin family. It is an α-2-globulin produced constitutively and released into the circulation mainly by the liver. AGT is an essential component of the renin-angiotensin system (RAS) and a potent regulator of blood pressure. AGT is cleaved into three chains: Angiotensin-1, Angiotensin-2, and Angiotensin-3. Defects in AGT are associated with susceptibility to essential hypertension and renal tubular dysgenesis (RTD). Several serpins (antithrombin, maspin, pigment epithelial-derived factor, and kallistatin) have been recently shown to exert an antiangiogenic activity, suggesting a common mechanism of endothelial cell proliferation and migration. Angiotensinogen/AGT and its renin-cleaved product, are also angiogenesis inhibitors, both in vitro and in vivo at concentrations within the range of those observed in plasma.