Since January 1980, 110 children having 113 attacks of Kawasaki syndrome were studied. Age at onset was 7 weeks to 12 years (mean 3 6/12 years, median 2 9/12 years); 77% were younger than 5 years of age; the male to female ratio was 1.8; racial distribution was 52% white, 19% black, 14% Hispanic, and 16% Asian. Protocol of management consisted of high-dose aspirin (100 mg/kg/d) until afebrile, and then 81 mg every day until free of coronary aneurysm. Two-dimensional echocardiograms were done weekly during the acute stage, at 2 and 6 months after onset, and yearly if a coronary abnormality was detected. At 1 month, 51 coronary arterial abnormalities were present in 25 patients. Risk factors for a coronary abnormality were duration of fever greater than or equal to 2 weeks, level of platelet count, marked elevation of ESR, and age younger than 5 years. No statistically significant difference in incidence of aneurysms was detected between patients on high-dose aspirin and those on medium-or low-dose aspirin.