Susceptibility to inflammatory bowel disease (IBD) has a strong genetic component. The vitamin D receptor (VDR) gene maps to a region on chromosome 12 shown to be associated with IBD in some studies. In this case-control study we determined the association between the BsmI VDR gene polymorphism and IBD in patients with Crohn's disease (CD) and ulcerative colits (UC). Three hundred seventy-nine Jewish Israeli patients with IBD, 228 with CD (129 Ashkenazi and 99 non-Ashkenazi), and 151 patients with UC (72 Ashkenazi, 79 non-Ashkenazi) were studied. The control group included 495 healthy blood donors (352 non-Ashkenazi and 143 Ashkenazi). All subjects were genotyped for the BsmI VDR gene polymorphism. The frequency of the BB genotype was higher in Ashkenazi patients with UC compared to Ashkenazi controls (0.21 vs. 0.11, p = 0.042, odds ratio 2.27, 95% confidence interval [CI] 1.06-4.9). There were no differences in the prevalence of the BB genotype or the B allele between ethnically matched patients with CD and UC. Nor were there differences in the BB genotype or B allele frequencies between CD patients and ethnically matched controls. The BsmI VDR gene polymorphism is associated with increased susceptibility to UC in Israeli Ashkenazi patients with UC.