We report four patients with Kawasaki disease in whom characteristic coronary artery abnormalities developed after illnesses that did not meet diagnostic criteria. An additional patient lacked a history of acute manifestations of Kawasaki disease, but severe Kawasaki-like arterial changes were noted at autopsy. Fever was present in four of the five patients, in three lasting from 7 to 14 days. Despite manifestation of few classic acute clinical features of Kawasaki disease, three of four patients had desquamation of the fingers and toes 10 to 14 days after onset of illness, and the fifth had desquamation several months prior to death. These patients were seen over a 2-year period during which 22 other children were seen with Kawasaki disease with coronary artery abnormalities. Thus, strict adherence to currently accepted criteria for diagnosis of Kawasaki disease may lead to failure to recognize incomplete forms of this illness, with potential sequelae of myocardial infarction or sudden death. This finding suggests that children with prolonged unexplained febrile illnesses, especially those associated with subsequent peripheral desquamation, should undergo echocardiography 3 to 4 weeks after onset of the illness. This practice would help to identify those patients with illnesses characterized by incomplete diagnostic criteria but in whom significant coronary abnormalities develop.