Angiopoietin 1 is one of the Angiopoietin (Ang) family of growth factors. It binds and activates the TIE2 receptor tyrosine kinase by inducing its tyrosine phosphorylation. It is implicated in endothelial developmental processes later and distinct from that of VEGF. The structure of angiopoietin 1 differs from that of known angiogenic factors or other ligands for receptor tyrosine kinases. Angiopoietin 1 appears to play a crucial role in mediating reciprocal interactions between the endothelium and surrounding matrix and mesenchyme. It also mediates blood vessel maturation/stability and it may play an important role in the heart early development. Angiopoietin 1 may have a potential therapeutic utility since it can be used for specifically targeting tumor vasculature or for promoting angiogenic processes in certain organs such as an ischemic heart.