A high activity glutathione S-transferase T1-1 (GSTT1-1) towards dichloromethane was isolated from human liver cytosol and purified to homogenity in 18.5% yield with a purification factor of 4400-fold. The GSTT1-1 was also isolated from erythrocytes, but the enzyme activity decreased rapidly in the final stages of purification. The purified GSTT1-1-s were homo-dimeric enzymes with a subunit M1 value 25,300 and pI 6 64, as confirmed by SDS-PAGE, IEF and Western blot analysis. The N-terminal amino acid sequences of GSTT1-1 from liver and red blood cells, analyzed up to the 12th amino acid, were identical. Immunoblot analysis revealed that GSTT1-1 was also present in lung, kidney, brain, skeletal muscle, heart, small intestine and spleen, but not in lymphocytes.