Background Nuclear factor-kB (NF-kB), a transcription factor, is a critical element regulating cell physiology and excessive NF-kB activation has been linked to cancer formation. NFKB1encodes NF-kB/p50 subunit. A common insertion (ins)/deletion ( del ) polymorphism (-94ins/delATTG) in NFKB1 promoter was recently found. It is reported that the ins allele may drive two-fold increase in NFKB1 transcription relative to del allele. Polymorphism of NFKB1 promoter was analyzed in patients with gastric cancer. Patients and methods To determine the -94ins/delATTG polymorphism in the NFKB1 promoter, DNAs from blood samples obtained from 182 gastric cancer patients and 263 controls were subjected to PCR-based genotyping. The primers generating amplicons of 305 (for del allele) or 309 bps (for ins allele) were sense: 5’-CCGCACCAAAAACCAGTAGAG-3’ and antisense: 5’-AGGGAGCCCCCAGGAAG-3’. The 5’ site of the sense primer was labeled with FAM fluorescence dye. The PCR products were subjected to DNA sequencer and the fluorescence were analyzed by Genescan. Results The alleotypic frequencies of NFKB1 ins is significantly higher in gastric cancer patients than controls (46.8% vs. 58.5%, p=0.0006), even adjusted with age and sex (p=0.024, OR: 1.64; 95% CI: 1.07-2.52). The frequency of genotype ins/ins is also significantly higher in patients with gastric cancer (p=0.029, OR: 2.57, 95%CI: 1.10-5.95). Conclusion The frequencies of alleotype NFKB1 ins and genotype ins/ins are significantly higher in gastric cancer patients and that suggest polymorphism of NFKB1 promoter is related to the risk of gastric cancer.