Prostate-specific membrane antigen (PSMA), also known as folate hydrolase 1 (FOLH1), is a type II transmembrane glycoprotein belonging to the M28 peptidase family. PSMA has two enzymatic activities, one as a prostate-specific integral membrane folate hydrolase and the other as a carboxypeptidase. An antibody to PSMA labels normal prostate epithelial cells and prostate tumor cells. Although the expression of PSMA in neovasculature of a variety of solid tumors has been reported, PSMA expression is highly restricted to the prostate. It is a useful marker for prostate tumors. In prostate cancer, overexpression of PSMA is correlated with high tumor grade, non-diploid tumors and advanced tumor state. It can be used as an effective predictor for tumor progression in prostate cancer.