AIM: To elucidate the possible difference in two promoter polymorphisms of the transforming growth factor-β1 (TGF-β1) gene (-800G > A, -509C > T) between ulcerative colitis (UC) patients and normal subjects.METHODS: A total of 155 patients with established ulcerative colitis and 139 normal subjects were selected as controls. Two single nucleotide polymorphisms within the promoter region of TGF-β1 gene (-509C > T and -800G > A) were genotyped using PCR-RFLP. RESULTS: There was a statistically significant difference in genotype and allele frequency distributions between UC patients and controls for the -800G > A polymorphism of the TGF-β1 gene (P < 0.05). The frequency of the TGF-β1 gene polymorphism at position -800 showed that the AA genotype and the allele A frequencies significantly differed between the patients and healthy controls (P < 0.05). At position -509, there was no statically significant difference in genotype and allele frequency between the patients and control subjects.CONCLUSION: The results of our study indicate that there is a significant difference in both allele and genotype frequency at position -800G > A of TGF-β1 gene promoter between Iranian patients with UC and normal subjects. AIM: To elucidate the possible difference in two promoter polymorphisms of the transforming growth factor-β1 (TGF-β1) gene (-800G> A, -509C> T) between ulcerative colitis (UC) patients and normal subjects. METHODS: A total of 155 patients with established ulcerative colitis and 139 normal subjects were selected as controls. Two single nucleotide polymorphisms within the promoter region of TGF-β1 gene (-509C> T and -800G> A) were genotyped using PCR-RFLP. was a statistically significant difference in genotype and allele frequency distribution between UC patients and controls for the -800G> A polymorphism of the TGF-β1 gene (P <0.05). The frequency of the TGF-β1 gene polymorphism at position -800 showed that the AA genotype and the allele A significant significantly differed between the patients and healthy controls (P <0.05). At position -509, there was no statically significant difference in genotype and allele frequency between the patients and control subjectes cts.CONCLUSION: The results of our study indicate that there is a significant difference in both allele and genotype frequency at position -800G> A of TGF-β1 gene promoter between Iranian patients with UC and normal subjects.