Altered expression of the facilitated glucose transporter GLUT1 affects pathways implicated in the pathogenesis of diabetic nephropathy. There is indication that variation of GLUT1 gene (SLC2A1) contributes to development of microangiopathy in diabetes mellitus type 2 (DM) patients. A genetic association study involving Caucasians was carried out to investigate the role of XbαI polymorphism in the GLUT1 gene in diabetic nephropathy (DN). Study population (n = 240) consisted of 148 unrelated patients with DM (92 cases with diabetic nephropathy (DN)), and of 92 matched healthy control subjects. Diabetic nephropathy was defined as persistent albuminuria (> 300 mg/24 h) and/or renal failure, in the absence of non-diabetes induced renal disease. The analysis showed that the risk of developing DM and DN in XbaI(−) carriers, when healthy individuals were considered as controls, was two-fold: odds ratio (OR) 2.08 [95% confidence interval (1.14–3.79)]. However, there was no evidence of association between XbaI(−) and DN when patients with DM and without DN were considered as controls: OR = 1.12 (0.55–2.26). Thus, the GLUT1 XbaI(−) allele is associated with DM, and possibly with a more severe form of the disease that can lead to development of DN.