Since its first description in Japan >30 years ago, Kawasaki disease (KD) has been reported worldwide. Although an infectious etiology is suspected based on the epidemiology and clinical features, a causative agent has not been identified. The disease is more frequent in children of Japanese ancestry, and siblings of children with KD have a significantly greater risk of developing KD than do children of the same age in the general population. This suggests a possible genetic susceptibility to KD. Results of this study showed that allele 1 of the 5' promoter (GT)n repeat in the SLC11A1 (formerly NRAMP1) gene, which endows the gene with a weak promoter activity, was highly represented in patients with KD. This suggests possible explanations for both the infectious etiology of this disease and the genetic risk in the Japanese population.