A body of evidence indicates obesity is an inflammatory state with chronic activation of the immune system. The interleukin 4 receptor (IL4R) single nucleotide polymorphism (SNP), rs 180275 (1902A>G) is well recognized for its association with atopy and other inflammatory diseases. We assessed the possible association of rs 180275 and rs 1805010 with obesity in Korean population. Study subject consisting of 876 Koreans were divided into three groups: subjects with 1) BMI<25, 2) BMI between 25 and 27, and 3) BMI>27. Analyses of genotype distributions and allele frequencies of study subjects revealed that rs 180275 polymorphism was associated with an increase in BMI in Korean population (P=0.009 and 0.011, respectively) while no association was found between rs 1805010 and obesity. We observed significantly lower percentage of rs 180275 G allele in subjects with BMI>27 than in subjects with BMI< or =27 (9.9% vs. 16.0%). Logistic regression analysis revealed that the odds ratio (OR) for an increase in BMI associated with the G vs. A allele was 0.57 [95% Confidence interval (CI)=0.39-0.85, p=0.002], which strongly implicates the protective role of rs 180275 G allele against an increase in BMI. Haplotype analysis revealed no association was present between rs 180275 and rs 1805010 polymorphisms. The frequency of rs 180275 G allele is significantly lower in subjects with BMI>27, suggesting the protective role of IL4R rs 180275 G allele against an increase in BMI in Korean population.