SERPINE1, also named as Plasminogen activator inhibitor type 1 (PAI-1), is a member of the serine protease inhibitor (SERPIN) superfamily. It is produced by the vascular endothelium, the liver, the monocytes/macrophagues, the platelets and the adipose tissue. High plasma levels of PAI-1 have been associated with an increased risk of suffering cardiovascular diseases. It is implicated in the pathogenesis of obesity, insulin resistance and type 2 diabetes. In several tumor types, SERPINE1 expression is up-regulated and it has been described as a poor prognostic marker. Besides its prognostic value, SERPINE1 expression has been validated as a marker for therapy decision making in patients with node-negative breast cancer. Defects in this gene are the cause of plasminogen activator inhibitor-1 deficiency (PAI-1 deficiency), and high concentrations of the gene product are associated with thrombophilia.