In a retrospective study conducted on a population of Japanese children with a weight ≥ 25 kg and with Kawasaki disease, no significant difference has been observed for the onset of coronary aneurysms, intravenous immunoglobulin (IVIg) resistance, duration of the hospitalisation and adverse treatment effects among the groups treated with 2 g/kg and 1 g/kg doses of IVIg. New randomised controlled studies are desirable to check the most appropriate IVIg dose for old children, also considering the cortisone treatment in association with the IVIg treatment firstly.