Glutamate carboxypeptidase II, also known as prostate specific membrane antigen or folate hydrolase I, is a type II transmembrane 750 amino acid membrane-bound glycoprotein, with a molecular weight in the human form of approximately 100 kDa and a demonstrated metallopeptidase activity. At the synaptic level it hydrolyzes N-acetylaspartylglutamate to N-acetyl-aspartate and glutamate. Its localization in the animal and human nervous system has only recently been clearly established, since many of the older studies gave conflicting results, likely due to the use of poorly characterized antibodies lacking epitope mapping and proper controls (i.e. immunohistochemistry complemented by western blot analysis and enzyme activity determination). In this chapter, we will review the available literature describing the animal and human distribution of glutamate carboxypeptidase in the central and peripheral nervous system.