Background/Aims: MCP-1 plays a pivotal role in inflammation and host response to infection by attracting mononuclear cells to tissues. Currently, striking evidence has been described that genetic polymorphism in the regulatory region of MCP-1 gene played a role in the pathogenesis of inflammatory bowel diseases. We have studied the expression of MCP-1 in UC patients and healthy controls to assess allelic frequency and genotypic distribution of the polymorphism (A/G) at position -2518 of MCP-1 promoter in patients with UC in Korean population. Methods: Forty-four patients, who were diagnosed with ulcerative colitis by endoscopic biopsy at Gastroenterology Clinic in Kyung Hee University Medical Center, and two hundred and forty-six healthy subjects were genotyped by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP). We compared the genotypes and allelic frequency of UC patients and controls. Results: Forty-four UC patients (32 males and 12 females: mean age, 48.0±13.6, range 28-80) and two hundred and forty-six healthy control subjects (80 males and 166 females: mean age, 51.0±12.6, range 30-81) were enrolled. G allele frequency in patients and controls were 45.55% and 60.13%, respectively. When the observed control and patient genotype frequencies were compared with expected values using 3×2 contingency table in the standard chi-square test, the genotype distributions in -2518 (A/G) of MCP-1 promoter for UC patients was significantly different (χ(2)=6.298, p=0.043). Compared with control data using 2×2 contingency table in the standard chi-square test, the frequency of A and G allele was also significantly different in UC patients (χ(2)= 6.626, OR=1.812, 95% CI=1.148-2.862, p=0.01). Conclusions: Genotype distributions and allelic frequencies in polymorphism of MCP-1 (-2518, A/G) were significantly different between UC patients and controls. This result is not consistent with previously reported frequency in Caucasian populations, which suggests the possible genetic heterogeneity between different ethnical groups in MCP-1 polymorphism. Larger-scale analysis on MCP-1 polymorphism from different ethnic patients is necessary to identify this issue. (Intest Res 2005;3:33-37)