Novel glutathione S-transferase (GST) isoenzymes, which do not bind to the glutathione (GSH) affinity column, were recently identified in dog kidney and dog renal cell lines. In humans, similar affinity flow-through GST has been previously found only in the urinary bladder. To ascertain whether these affinity flow-through GST isoenzymes also exist in the human kidney, we separated GST isoenzymes from five kidney samples on the basis of their affinity to GSH affinity resin. GSTs were further purified by anion exchange chromatography and chromatofocusing and characterized with specific substrates. Our results show that the human kidney has both affinity flow-through GST isoenzymes and those which bind tightly to the GSH affinity column. Purification of affinity-bound GST resulted in a rich profile of different isoenzymes with balanced expression of both anionic and cationic forms. Affinity flow-through GST was represented by one isoenzyme (pI-7.9) in all kidney samples tested, but one kidney specimen also contained another GST isoenzyme (pI-7.0). Our results for the first time show the presence of GST isoenzymes that do not bind to GSH-affinity resin in the human kidney. Although the assessment of similarity between the human kidney and urinary bladder affinity flow-through GST requires further elucidation, it can be speculated that these particular GSTs may play an important role in providing protection against the common carcinogens.