Alopecia areata (AA) is a chronic inflammatory disease with evidence of T-cell involvement that causes hair follicle "immune privilege collapse". Nitric monoxide was shown to contribute in the pathogenesis of AA. We are investigating evidence for the association of eNOS gene polymorphism with AA. Genomic DNA was extracted from 176 subjects, 87 Kuwaiti AA patients and 89 matched (for ethnicity, gender and age) healthy controls. A variable number tandem repeat (VNTR) located in intron-4 of the eNOS gene consisting of either four or five (27-base pair) repeats was analyzed by polymerase chain reaction and electrophoresis fragment analysis using ABI 3100 genetic analyzer. Haploview and GenePOP software were used for data analysis. A significant association was found between the intron-4 27 bp-VNTR and AA, where 4b was identified as the risk allele had (chi(2) = 4.42, p = 0.035, OR = 2.03). Genotype (4b/4b) showed a significant association with susceptibility to AA and have a frequency of 22% higher in AA patients than in healthy controls (71 vs 49%) and a chi(2) = 6.39, (p = 0.011, OR = 2.63). We report a significant association of a polymorphism within the eNOS gene and susceptibility to AA.