Using a PCR-RFLP assay, a total of 216 Russian type 1 diabetic (T1D) patients with DN and 250 T1D individuals without DN have been tested to verify whether the -262T > C and 1167C > T polymorphisms of the catalase (CAT), 197Pro > Leu amino acid substitution of the glutathione peroxidase 1 (GPX1) and +/null polymorphism of the glutathione S-transferase M1 (GSTM1) and T1 (GSTT1) genes contribute to susceptibility to DN.