Genetic predisposition has been implicated in diabetic nephropathy. The C677T variant of the MTHFR gene has been suggested to play a role in the development of not only vascular diseases but also diabetic microangiopathies. By using polymerase chain reaction-restriction length polymorphism (PCR-RFLP) method using Hinf I, we investigated whether this variant is associated with diabetic nephropathy in Japanese. By analysing 274 unrelated Japanese patients with type II DM with or without nephropathy, there was no significant difference in the genotype distribution of this variant. The distribution of the three genotypes were not different among patients with micro- or macroalbuminuria and those without nephropathy. Although previous reports suggest a role of this variant with diabetic microangiopathies, our observations suggest that this variant is does not play an important role in the pathogenesis of diabetic nephropathy in Japanese.