Angiopoietin-2 (ANG-2) is an approximately 70 kDa secreted glycoprotein that plays a complex role in angiogenesis, inflammation, and vascular development. It is expressed in vascular endothelial and smooth muscle cells in highly angiogenic tissues, lung epithelial cells, differentiating myotubes, and neural progenitor cells. ANG-2 promotes endothelial cell survival, proliferation, and migration, and also promotes sprouting angiogenesis. It induces the loss of pericytes from vessel walls and an increase of vascular permeability. ANG-2 is required for the development of lymphatic vessels as well as the postnatal remodeling of both lymphatic and vascular vessels.

ANG-2 is elevated in patients with angiosarcoma. Research on ANG-2 has shown that it is involved in the onset of septic shock. Serum levels of ANG-2 expression are associated with the growth of multiple myeloma, angiogenesis, and overall survival in oral squamous cell carcinoma. Circulating ANG-2 is a marker for early cardiovascular disease in children on chronic dialysis. Kaposi's sarcoma-associated herpesvirus induces rapid release of ANG-2 from endothelial cells.