Glutathione S-transferases (GSTs) are a family of multifunctional detoxifying enzymes that catalyse the conjugation of glutathione with large number of compounds bearing an electrophilic center, including carcinogens, and also bind a variety of nonsubstrate ligands. The transferases are widely distributed in the mammalian species and can be grouped into three classes on the basis of subunit composition: alpha (basic), mu (neutral), and pi (acidic). The liver is an organ possessing abundant GST-alpha. GST-mu is also present in the liver and lymphocytes, but this is absent in approximately 50% of the human population. GST-pi (originally found in the placenta) is widely located in the lung, kidney, GI tract, erythrocytes and cancer cells. The present review describes a new nomenclature of human GST isoenzymes and recent investigations of this enzymes, including ours. Implications of each isoenzyme are also discussed.