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 percent of the patients die suddenly from acute heart failure. Infantile polyarteritis (nodosa-like arteritis) accompained 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.