Glutathione transferase (GST) was investigated with 1-chloro-2,4-dinitrobenzene as substrate in tissues specimens of human nasal mucosa. The average +/- (SD) of GST activity in the cytosol was 76.8 +/- 21 nmol/min/mg with a range of 47-113. Using affinity chromatography and isoelectric focusing, the isozymes of GST from human nasal mucosa have been purified and characterized. On the criteria of isoelectric point, substrate specificities, apparent subunit molecular weight, sensitivity to characteristic inhibitors and immunological properties the major GST purified (about 85% of total activity) can be identified as class pi GST. Although a limited amount of class alpha GST was expressed by human nasal mucosa, no class mu isoenzymes was noted. In addition, we have also identified a GST subunit that cannot be related to any of three major classes of human GST.