PURPOSE: Hyperhomocysteinemia is known as an independent risk factor for cardiovascular diseases such as atherosclesosis and myocardiac infarct. A common mutation in 5, 10-methylenetetrahydrofolate reductase(MTHFR) gene results in a valine for alanine substitution, which makes enzyme thermolabile and reduces enzymal activity. We examined the relation of MTHFR genetic mutation and Kawasaki disease. METHODS: We extracted DNA from the peripheral blood of Kawasaki disease patients who were treated in Ewha University Mokdong Hospital between January 2000 and June 2003, and normal children. We genotyped for the polymorphism by using PCR of known alleic varients and digested them with Hinfl restriction enzyme. Products were visualized after electrophoresis in 2.5% agarose gel. RESULTS:The respective prevalence of the homozygous and heterozygous genotypes(CC genotype, CT genotype, TT genotype) was 33.3%, 38.9%, and 27.8% in the control group and 31.3%, 47.9%, and 20.8% in the Kawasaki disease group(P>0.05). CONCLUSION:The mutation of MTHFR gene shows no relation to development of coronary artery complications in Kawasaki disease.