Metabolic syndrome (MetS) is rapidly growing into one of the major public health issues worldwide. Interleukin 1 receptor antagonist (IL1Ra) functions as a competitor of proinflammatory cytokines and has an important role in metabolic functions, including insulin secretion. To identify the relationship between the interleukin 1 receptor antagonist gene (IL1RN) and MetS, we genotyped nine single nucleotide polymorphisms (SNPs) in the gene using direct sequencing in 66 MetS patients and 346 normal subjects in the Korean population. Among the nine polymorphisms, after adjusting for age and sex, rs928940 (G>T) showed a significant association with MetS in the codominant ( P= 0.023) and recessive models ( P= 0.011). Also, rs315952 (C>T) exhibited a significant association with MetS in the codominant model ( P= 0.046). The results suggest that the IL1RN polymorphisms may be associated with MetS in the Korean population.