The products of three human glutathione S-transferase (GST) loci (GST1, GST2 and GST3) were purified and their immunochemical properties as well as immunohistological localization in liver were studied. Three group of isozymes were different in molecular weight, substrate specificities and antigenicity. Two homodimers (type 1 and type 2) of GST1 which shows genetic polymorphism, were similar in immunochemical properties other than isoelectric point. Inactivity of GST1 0 was due to impaired protein synthesis. Immunohistologically, GST1 isozyme was homogeneously stained in cytoplasm of hepatocytes throught the lobule of liver showing GST1 1, GST1 2 and GST1 2-1 phenotypes. On the other hand, GST2 isozyme was stained in the cytoplasm as well as the nucleus of hepatocytes throughout the hepatic lobule in all cases. GST3 isozyme was strongly stained in biliary epithelium. These results indicate that the human liver GSTs are composed of three immunochemically distinct isozymes, which exhibit significant difference in inter-individual, specific cellular and organellar distribution.