Kawasaki disease (KD) is a leading cause of acquired heart disease in children of developed countries. Intravenous immune globulin (IVIG) at 2g/kg is effective in the rapid resolution of KD inflammation. However, approximately 15 to 20% of patients had persistent or recurrent fevers after IVIG completion and are considered to have a higher risk of developing coronary aneurysms. The management of these IVIG-resistant patients is unestablished. Recently, Onouchi Y et al. identified a significant functional SNP in the inositol 1,4,5-triphosphate 3-kinase C (ITPKC) gene which was associated with KD susceptibility. ITPKC acts as a negative regulator of T-cell activation through the Ca2+/NFAT signaling pathway. Importantly, Cyclosporin A (CsA) suppresses T-cell activation by blocking downstream molecule of Ca2+/NFAT pathway. Then, we sought to determine effects of CsA on clinical outcome in IVIG-resistant patients. Sixty-two patients admitted to our hospital from January 2008 through December 2008 were initially treated with IVIG plus aspirin. Of these patients, 12 patients (19.3%) were resistant to initial treatment. Then, all 12 patients received re-IVIG at 2g/kg. Consequently, 6 patients (9.6%) resistant to re-IVIG were additionally treated with CsA at 4mg/kg orally for 3 weeks. Five of the 6 patients responded to CsA and had normal coronaries, but the remaining one had persistent fever despite of increased dose of CsA up to 8mg/kg and developed moderate size (4-5mm) of aneurysms in both coronary arteries. Significant adverse effects of CsA have not been documented. CsA may be one of effective treatment for refractory KD.