Background and aims: Vitamin D deficiency has been identified in the elderly as a potential risk factor for cardiovascular disease development, possibly through its association with other risk factors, such as type 2 diabetes mellitus (T2DM), hypercholesterolemia and hypertension. The aim of this cross-sectional study was to evaluate the vitamin D status in elderly subjects with impaired fasting glucose (IFG) or T2DM, and to examine its relationships to systemic oxidative stress and biochemical markers of endothelial dysfunction. Methods: Serum 25-hydroxyvitamin D [25(OH)D], fasting glucose, insulin, lipid profile, advanced glycation end products (AGEs), advanced oxidation protein products (AOPPs), low-density lipoprotein susceptibility to oxidation (oxLDL) and nitric oxide metabolic pathway products (NOx) were analyzed in elderly subjects with IFG (n=30) and T2DM (n=35) compared with aged-matched controls (n=25). Results: 25(OH)D levels in the IFG and T2DM groups were significantly lower than in controls (31.9±1.9 and 28.5±1.9 vs 39.4±2.4 ng/mL, p<0.001), and associated with significantly (p<0.001) higher levels of the oxidative stress parameters AGEs, AOPPs, oxLDL and NOx. Hypovitaminosis D [25(OH)D)>-30 ng/ml] markedly enhanced the oxidative stress and cardiovascular risk in hyperglycemic subjects compared with sufficient vitamin D [25(OH)D)=30 ng/mL] status subjects. In subjects with IFG and T2DM (n=65), the vitamin D status was significantly inversely correlated both with oxLDL (r=−0.413, p=0.001) and AOPPs (r=−0.475, p<0.001), and strongly positively associated with highdensity lipoprotein cholesterol (r=0.609, p<0.001). Conclusions: In the elderly with impaired glucose metabolism the vitamin D status is inversely associated with levels of circulating markers of oxidative stress and endothelial dysfunction, especially in subjects with hypovitaminosis D.