Migraine is considered to be a polygenic multifactorial disease with various environmental and genetic etiologies. Tumor necrosis factor-alpha (TNF-alpha), a potent immunomodulator and pro-inflammatory cytokine, has been implicated in many pathological processes in brain. The hypothesis of this study was that migraine without aura (MWA) might be associated with TNF-alpha (-308) polymorphism, resulting in increased TNF-alpha production. Genotyping was performed on DNA extracted from peripheral leukocytes by PCR-SSP method in 221 patients with WMA and 183 healthy control subjects from Iranian population. The results showed that the frequency of -308 A variant allele was higher in MWA than in the control group (40.6% versus 22.3%, OR 3.73, 95% CI 2.4-5.82, p<0.0001). TNF-alpha GA heterozygous genotype, high producer, was significantly more prevalent in patients with MWA than controls (74% versus 44.7%, p<0.0001) whilst the low producer GG homozygous genotype was less frequent in patients compared with controls (22.4% versus 55.3%, p<0.0001). The logistic regression analysis showed a significant association for TNF-alpha (-308A) female allele carriers with MWA at reproductive ages (OR 2.56; 95% CI, 1.57-4.16, p<0.0001) when compared with their matched control subjects. In conclusion, this study demonstrates an association of tumor necrosis factor-alpha (-308A) carriage with MWA, suggesting that carrying a high responder TNF-alpha-308A allele may be a genetic factor in increasing the susceptibility to develop MWA.