The aim of this study was to investigate the relationship between MTHFR, IRS and CALCA gene polymorphisms and development of diabetic nephropathy (DN) in patients with type 2 diabetes mellitus (DM). Our study included 93 patients with type 2 DM diagnosed as having nephropathy and 95 controls diagnosed with type 2 DM without development of DN. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to determine the genotype distributions of MTHFR, IRS and CALCA gene polymorphisms. The results showed no statistically significant difference between DN patients and type 2 DM controls in