Kawasaki disease (KD) is now the most common cause of acquired heart disease in children in the United States and in Japan. Despite 20 years of research since the first English-language report of KD, the etiology of this disease continues to elude us. The long-term effects of the acute vasculitis on the health of the coronary arteries in adulthood is similarly unknown. A review follows of the progress that has been made in our understanding of the pathogenesis and treatment of this mysterious illness.