Previous studies revealed that there were various mutations on endothelial nitric oxide synthase (eNOS) gene and these mutations might be a risk factor for coronary artery disease (CAD), myocardial infarction (MI), and hypertension (HT). In this study, we aimed to investigate the relationship between eNOS gene polymorphism (T-786 C) and coronary artery disease in the Turkish population. Two hundred and eleven unrelated individuals (152 male, 59 female, mean age 59 years, range 27-85) whose angiographic examinations were performed in our hospital were enrolled into the study; 159 of these had angiographically determined coronary artery lesions (>or=50% stenosis at least in one vessel). Fifty-two individuals were free of coronary artery disease on their coronary angiography. The Gensini scoring system was used to determine the severity of the CAD. The polymerase chain reaction (PCR) method was used for genotyping the individuals. To determine the independent risk factors for coronary artery disease, multivariate logistic regression analysis was used. The variant distribution of the T-786 C polymorphism was as follows. For all individuals: TT 94 (44.5%), TC 88 (41.7%), CC 29 (13.8%); in CAD patients: TT 63 (39.6%), TC 73 (45.9%), CC 23 (14.5%); and in normal individuals: TT 31 (59.6%), TC 15 (28.8%), CC 6 (11.5%). There was a statistically significant difference in the variant distribution between CAD and normal individuals (P<0.05). On the other hand, when we compared the frequency of the at-least-one-C-allele carriers (CC+TC, dominant model) and TT homozygous, those with at least one C allele were more prevalent in CAD patients. The results were as follows. In coronary artery disease patients: CC+TC 96 (60.4%), TT 63 (39.6%); in normals: TC+CC 21 (40.4%), TT 31 (59.6%) (P<0.01). When we compared the allele distribution (T vs C, additive model) between CAD patients and normal controls, the results were as follows: T 0.625 vs 0.740, C 0.375 vs 0.260; there was also a statistically significant association between CAD and C allele (P<0.05). When we compared the means of the Gensini scores between each genotype of the T-786 C mutation, there was a statistically significant difference. The results were TT (48.6+/-37.3, median 43.0), TC (55.4+/-41.2, median 41.0), CC (77+/-43.6, median 80.0) (P<0.05). Multivariate logistic regression analysis revealed that C-dominant (CC+TC) individuals had 2.9-fold more likelihood to suffer from CAD (odds ratio: 2.902; confidence interval: 1.272-6.622) (P<0.05). We conclude that the T-786 C polymorphism of eNOS gene might be a risk factor for coronary artery disease in the Turkish population.