Tumour necrosis factor (TNF)-α is an important pro-inflammatory cytokine that has been implicated in the pathogenesis of inflammatory bowel disease (IBD). The promoter TNF-857 C→T single nucleotide polymorphism (SNP) is functional through the binding to the transcription factor octamer transcription factor-1 (OCT-1). In order to investigate the frequency of this SNP in Israeli Jewish IBD patients, we analysed a cohort of well-characterized patients, 153 with Crohn's disease (CD) and 78 with ulcerative colitis (UC) and 188 healthy controls individually matched for age, sex and ethnicity. Forty-one per cent of the patients were of Ashkenazi and 48% were of non-Ashkenazi background. The remaining 11% were of mixed Ashkenazi-non-Ashkenazi background. Patients and controls were genotyped for the TNF-857 SNP by Taqman technology. Stratification for the CARD15 Arg702Trp, Gly908Arg and Leu1007fsinsC mutations took place in 136 CD patients. Carrier frequency of TNF-857T between CD and controls (36% vs. 40%; P = 0.556; OR: 1.18, 95% CI 0.74-1.88), or between UC and controls (41% vs. 37%; P = 0.743; OR: 0.85, 95% CI 0.45-1.62) did not differ significantly. Neither did stratifying for the presence of at least one of the common CARD15 mutations result in a significant difference between CD and controls. No associations were found between TNF-857T and CD phenotype as defined by the Vienna classification, perianal disease or extra-intestinal disease irrespective of CARD15 carrier status. In conclusion, it appears that TNF-857 SNP does not contribute to susceptibility of IBD, neither does it define the phenotype of CD in Israeli Jewish IBD patients.