AIM: To investigate the frequency and distribution of N-acetyltransferase 2 (NAT2) and uridine 5′-diphosphate (UDP)-glucuronosyltransferase 1A7 (UGT1A7) genes in patients with ulcerative colitis (UC) and Crohns disease (CD).METHODS: Frequencies and distributions of NAT2 and UGT1A7SNPs as well as their haplotypes were investigated in 95 patients with UC, 60 patients with CD, and 200gender-matched, unrelated, healthy, control volunteers by PCR-restriction fragment length polymorphism (RFLP),PCR-denaturing high-performance liquid chromatography (DHPLC), and direct DNA sequencing.RESULTS: Multiple logistic regression analysis revealed that the frequency of haplotype, NAT2*7B, significantly increased in CD patients, compared to that in controls (P= 0.0130, OR = 2.802, 95%CI = 1.243-6.316). However,there was no association between NAT2 haplotypes and UC, or between any UGT1A7haplotypes and inflammatory bowel disease (IBD).CONCLUSION: It is likely that the NAT2 gene is one of the determinants for CD in Japanese. Alternatively, a new CD determinant may exist in the 8p22 region, whereNAT2is located.