Background: Glutathione transferases (GSTs) are enzymes involved in the cell detoxification. Increased levels of GST expression have been observed in tissues exposed to contaminants and in human erythrocytes of uremic patients under chronic hemodialysis (HD). A previous study reported that no difference in the erythrocyte GST expression has been detected in patients under conservative therapy. Aim of our study was to compare erythrocyte GST (e-GST) activity in chronic kidney disease (CDK), in chronic hemodialysis (HD) and in healthy subjects. Methods: A total of 72 CKD patients under conservative therapy, 62 HD patients and 80 healthy subjects were enrolled. CKD patients were divided in four groups according to the National Kidney Foundation Dialysis Outcomes Quality Initiative (NK-DOQI). Erythrocyte GST activity was assayed by means of a spectrophotometer procedure at 340 nm on haemolysed whole blood adapted to an automated Modular P800 apparatus (Roche). Results: The e-GST activity was enhanced in HD patients (10.24± 2.74 U/g Hb) when compared to healthy subjects (5.8±1.8 U/g Hb). Contrary to previous reports, a significant increase of e-GST activity related to CKD stage was also observed in pre-dialysis patients (7.4± 2.43 U/g Hb, 8.13±4.55 U/g Hb, 9.46±2.49 U/g Hb, and 12.35± 2.74 U/g Hb in stages I to IV). Interestingly, e-GST activity in stage IV patients is higher than in HD subjects. No correlation has been found between e-GST activity and levels of classical systemic inflammation markers. Conclusion: The present findings suggest that e-GST could be a good marker for toxin exposition. The e-GST activity could be a new biomarker useful to substitute or to be complementary to the time.