Aim:The aim of this study was to investigate the association of T-786C, G894T and 4a/b polymorphisms in the endothelial nitric oxide synthase (eNOS) gene with early-onset ischemic stroke in South Indians. Methods: We enrolled 177 patients diagnosed with ischemic stroke aged between 15 to 45 years and 219 age-and gender-matched healthy controls. Genotypes of eNOS T-786C, G894T and 4a/b were identified by polymerase chain reaction and restriction fragment length polymorphism. Results: The allele and genotype frequencies of eNOS 4a/b, T-786C and G894T did not differ significantly in the patient group compared to controls. Logistic regression analysis indicated the 4a allele to be an independent predictor of ischemic stroke in females (dominant model: OR, 2.46; 95% CI, 1.11 to 5.43; p 0.026). Marked differences were found in the prevalence of the minor alleles of the three variants when comparing the South Indian population with the reported frequencies from Caucasians. There was also a contrast in the frequencies of 4ab and T-786C variants from other Asians. The genotypes of all three variants were found to be in Hardy-Weinberg equilibrium. There was a lack of significant linkage disequilibria among the variants, and none of the estimated haplotypes increased or decreased the risk of ischemic stroke. Conclusion