Kawasaki recognized in 1967 the acute febrile mucocutaneous lymph node syndrome (MCLS) as a well defined entity among a variety of hitherto unidentified atypical exanthems. The etiology is uncertain. There are close relations to infantile polyarteritis nodosa (IPN) which is probably the severe variant of Kawasaki's disease. Histologically it is a generalized necrotizing vasculitis, most probably caused by circulating immune complexes. The disease is supposed to be initiated by various infections in patients with certain predispositions. Considerations about etiology and pathogenesis as well as relations to IPN are mainly discussed theoretically. Therefore it is recommended to investigate the Kawasaki syndrome following a devised protocol.