Phase I was randomized, unblinded and stratified by age, sex, and center. Subjects were randomized to receive either 80 to 120 mg/kg/day of aspirin through day 14 of illness, subsequently reduced to 3 to 5 mg/kg/day as a single daily dose or to 400 mg/kg/day of intravenous gamma globulin for four consecutive days plus aspirin as above. Primary endpoint was formation of aneurysms as demonstrated by echocardiograms. Follow-up was for 7 weeks.