In 1967, Kawasaki, in Japan, first described a new syndrome affecting infants and young children—an acute, febrile illness with mucocutaneous involvement associated with swelling of cervical lymph nodes. The prognosis is usually good but recently it has become evident that 1–2% of the patients die suddenly from acute heart failure. Infantile polyarteritis (nodosa-like arteritis) accompanied by coronary aneurysm and thrombosis has been noted in postmortem examinations. Twenty patients surviving the illness were examined by coronary angiography; 12 of the 20 had abnormal coronary angiograms; seven patients had coronary aneurysms. Complete regression of the coronary aneurysms was proved in two patients at subsequent angiography. One patient developed mitral regurgitation as a result of papillary muscle dysfunction. One had a coronary aneurysm without symptoms two years after the onset of illness.