ABSTRACT: To clarify the association between a polymorphism -449 C>G (rs72696119) in 5'-UTR of NFKB1 with ulcerative colitis (UC).The studied population comprised 639 subjects, including patients with UC (UC cases, n = 174) and subjects without UC (controls, n = 465). We employed polymerase chain reaction-single strand conformation polymorphism to detect the gene polymorphism.The rs72696119 G allele frequencies in controls and UC cases were 33.4% and 38.5%, respectively (P = 0.10). Genotype frequency of the GG homozygote in UC cases was significantly higher than that in controls (P = 0.017), and the GG homozygote was significantly associated with susceptibility to UC [odds ratio (OR), 1.88; 95%CI, 1.13-3.14]. In male subjects, the GG homozygote was associated with an increased risk for UC (OR, 3.10; 95%CI, 1.47-6.54; P = 0.0053), whereas this association was not found in female subjects. In addition, the GG homozygote was significantly associated with the risk of non-continuous disease (OR, 2.06; 95%CI, 1.12-3.79; P = 0.029), not having total colitis (OR, 2.40; 95%CI, 1.09-3.80, P = 0.040), disease which developed before 20 years of age (OR, 2.80; 95%CI, 1.07-7.32, P = 0.041), no hospitalization (OR, 2.28; 95%CI, 1.29-4.05; P = 0.0090) and with a maximum of 8 or less on the UCDAI score (OR, 2.45; 95%CI, 1.23-4.93; P = 0.022).Our results provide evidence that NFKB1 polymorphism rs72696119 was significantly associated with the development of UC. This polymorphism influences the susceptibility to and pathophysiological features of UC.