Angiopoietin-2 (ANG-2) is a secreted glycoprotein with a molecular weight of approximately 70 kDa. It has complex roles in angiogenesis, inflammation, and vascular development, and is expressed in endothelial cells, smooth muscle cells, pulmonary epithelial cells, differentiated myotubes, and neural precursor cells in highly vascularized tissues. ANG-2 promotes the survival, proliferation, and migration of endothelial cells and facilitates sprouting angiogenesis while inducing loss of perivascular cells and increasing vascular permeability. ANG-2 is essential for lymphatic vessel development and postnatal remodeling of both lymphatic and blood vessels.Patients with vascular tumors have elevated levels of ANG-2 in their bloodstream, and studies have shown that ANG-2 is involved in the pathogenesis of septic shock. The expression of ANG-2 in serum is associated with the growth of multiple myeloma, angiogenesis, and overall survival in oral squamous cell carcinoma. Circulating ANG-2 has been identified as a biomarker of early cardiovascular disease in children undergoing chronic dialysis, and capillary leak syndrome induced by Kaposi’s sarcoma-associated herpesvirus leads to rapid release of ANG-2 from endothelial cells.