Serpin E2 is a member of the Serpin superfamily of the serine protease inhibitors. Serpin E2 is apotent inhibitor of thrombin, plasmin and plasminogen activators. It is differentially expressed during neuronal differentiation and is able to transform humanembryonic kidney cells into neuronlikecells. Its over-expressionin mice leads to progressive neuronal and motor dysfunction in these animals. It is also over-expressedin the majority of pancreatic carcinoma as well as gastric and colorectal cancer samples whereas it is weakly expressed in all normal pancreas and chronicpancreatitis tissue samples. It plays an important role in controlling male fertility because its knockout male mice show a marked impairment in fertility from theonset of sexual maturity and its abnormal expression is found in the semen of men with seminal dysfunction.