Little it is known about the association of endothelial nitric oxide synthase gene (NOS3) polymophisms and the presence of insulin resistance and atherosclerosis in non diabetic subjects with cardiovascular disease (CAD) and stent implantation. The present study was performed to better understand whether metabolic, endothelial and angiographic findings characteristic of subjects with cardiovascular disease and in-stent restenosis are related to NOS3 variants. This is a case-control study performed from 2002 to 2006. All subjects admitted to the study were recruited in the Nord-Centre of Italy, most from Milan and its surrounding towns. Measures of glucose tolerance, insulin sensitivity, markers of endothelial dysfunction, forearm vasodilation, and adipokine levels were determined and associated to the frequency of two SNPs of NOS3, i.e. Glu298Asp (rs1799983, G/T) and rs753482 (intron 18 A/C). A total of 747 subjects, not known to have diabetes, were evaluated: 333 subjects had asymptomatic CAD, 106 subjects had unstable angina and were evaluated for in-stent restenosis six months after stent placement and 308 were control subjects. The presence of TT and CC minor alleles was significantly greater in case groups compared to control subjects. At phenotypic level, subjects with the polymorphisms were characterized by hyperinsulinemia, reduced reactive hyperemia while increased leptin and decreased adiponectin levels were present in subjects with restenosis in the presence of reduced minimal lumen diameter and length of stenosis almost doubled. Hyperinsulinemia, endothelial dysfunction and a more atherogenic profile seems to be a peculiar feature of subjects with asymptomatic CAD and restenosis carrying NOS3 gene variants.