It has become unusual in modern medicine for a serious, presumably infectious disease to defy virtually all efforts at elucidation of its etiology and pathogenesis and to leave unanswered, after two decades, so many questions about therapy and prognosis. Other newly described mysteries, including legionnaires' disease, toxic shock syndrome, Lyme disease, and even the acquired immunodeficiency syndrome, have been solved, or at least "demystified," with impressive regularity, but Kawasaki syndrome has not. Kawasaki syndrome was first described in the 1960s in Japan, where it continues to be highly prevalent. 1 A decade later, cases were recognized (independently) in Hawaii, 2 and in recent years, epidemics have occurred in several American cities. 3 Primarily affecting young children, the disease is characterized by fever, conjunctival injection, oropharyngeal inflammation, peripheral extremity changes (edema, erythema, and desquamation), rash, and cervical lymphadenopathy. Coronary artery aneurysms have been present in 7% to 40% of cases, with an