Kawasaki syndrome is a newly described, acute symptom complex of children that has a predictable clinical course. The acute febrile phase of the syndrome is characterized by multisystem acute inflammatory changes. The subacute phase follows with the rheumatic manifestations of arthritis, myocarditis, and thrombocytosis. The syndrome is self-limited in most children but is associated with coronary artery aneurysms in 15%--20% and sudden death due to coronary thrombosis in 2%. Vasculitis of coronary and other medium-sized muscular arteries characterizes fatal cases. The peak age affected is 12 months (range, six weeks to eight years). Japanese children are overrepresented among cases, whereas Caucasian children are underrepresented. Cases have been reported worldwide with the highest prevalence in Japan and among Japanese in Hawaii. Epidemic outbreaks have occurred in scattered areas of the United States and Japan. The etiology is unknown, although clinical, epidemiologic, and immunologic features suggest an acute infectious trigger to an immunologically mediated, generalized vasculitis.