Kawasaki's syndrome is an acute, largely self-limited multisystem vasculitis of childhood with prominent rheumatic complaints, involving both the heart and the joints. Although the etiologic agent has not been discovered, the evidence appears overwhelming that a microbial agent is the responsible trigger for this multisystem disease. Immunologically mediated phenomena appear to be important in the development of the significant complications of KS carditis, coronary vasculitis, and arthritis. Although truly effective therapy is not yet available, there is an exciting possibility that immunologic treatment may have beneficial effect. More effective preventive and therapeutic methods will become available when the elusive agent is discovered.