BACKGROUND: Oxidative stress may be a determinant of the development of diabetic nephropathy. Glutathione S-transferases(GST) can work as an endogenous antioxidant to protect cells from oxidative stress. Homozygous deletion of the mu and theta subclasses of GST(GST-M1 and GST-T1), and Val105Ile polymorphism of the pi subclass of GST(GST-P1) are associated with antioxidant enzyme activity. In this study, whether the Val105Ile of GST-P1, null genotype of GST-M1 and GST-T1 are associated with type 2 diabetic nephropathy were examined. METHODS: These GST subclasses were genotyped in 361 type 2 diabetic patients with retinopathy; the subjects were divided into two groups, those with an end stage renal disease(ESRD)(the case group n=177) and those(the control group, n=184) showing no signs of renal involvement. RESULTS: The frequencies of the GST-P1 Ile105Val and GST-T1 null genotypes were no different between the cases and controls. However, the frequency of the GST-M1 null genotype was significantly higher in the cases than the controls(61.7% vs. 51.1%, chi-square=4.09, P=0.043), which was still significant after correction for age, sex and duration of diabetes (P= 0.044). In addition, the GST-M1 null genotype showed an increased frequency between the controls and the cases with long and short durations of type 2 diabetes until the onset of ESRD(51.1, 58.9 and 65.5%, respectively; chi-square for trend=5.12, P=0.024). CONCLUSION: This is the first study to suggest that the GST-M1 gene polymorphism might contribute to the development of ESRD in type 2 diabetic patients.