gamma-Glutamyltransferase(GGT: E.C. 126.96.36.199.) is a glycoprotein enzyme which is involved in glutathione metabolism and amino acid transport through the plasma membrane. It is distributed widely in several organs including liver, kidney, pancrease and brain. GGTs derived from the brain of Wister rats and BALB/c mice were biochemically purified to a specific activity of 4246.2, 862.1 units per mg of protein, a purification folds 93.7, 43.8 and the final yield 65.8, 44.0% respectively. Electrophoretic pattern of purified GGTs from rats and mice brain shows very similar protein fraction each other. We have produced six monoclonal antibodies(GGT-Mab 1-6) against 2-acetamidogluorene treated rat liver GGT. Using these GGT-Mab 1-6 we performed immunohistochemistry(IHC) to study the distribution of GGT isozymes in normal tissues of rat brain and in neoplastic tissues of human brain. The results indicated that human brain GGT was localized in pericytes of blood-brain barrier, especially in the blood-rich portion of the brain(e.g. cerebellum of rat, meningioma and craniopharyngioma of human). Therefore these Maps may be used to evaluate the distribution of GGT isozymes in different tissues.