The efficacy of intravenous gamma globulin (IVGG) for treatment of Kawasaki disease (KD) is clearly established. In a metaanalysis, we reviewed U.S. and Japanese multicenter, randomized controlled studies regarding the effect of various doses of IVGG with aspirin administered within the first 7 to 10 days of illness on the prevalence of coronary artery abnormalities in KD. We studied 1629 patients with acute KD from the sir: reported studies that included blinded echocardiographic assessments. In 868 Japanese patients treated with moderate-dose aspirin (30 to 50 mg/kg per day), the prevalence of coronary abnormalities at the subacute stage (illness day 30) was 26.8% with aspirin alone, 18.1% with total IVGG dose < 1 gm/kg, 17.3% with total IVGG of 1.0 to 1.2 g/kg, and 5.3% with total IVGG of 2 gm/kg; the corresponding prevalence at the convalescent stage of illness (illness day 60) was 17.5%, 13.5%, 9.8%, and 3.5%, respectively. In 761 U.S. patients treated with high-dose aspirin (80 to 120 mg/kg per day), the prevalence of coronary abnormalities at the subacute stage (2 to 3 weeks after enrollment) was 23.0% with aspirin alone, 9.0% with total IVGG of 1.0 gm/kg, 8.6% with total IVGG of 1.6 gm/kg, and 4.6% with total IVGG of 2.0 gm/kg; corresponding prevalence at the convalescent stage (6 to 8 weeks after enrollment) was 17.7%, 9.0%, 6.3%, and 3.8%, respectively. When all data for the 1629 patients were combined, the prevalence at. the subacute stage was 25.8% with aspirin alone, 18.1% with IVGG < 1 gm/kg, 15.7% with IVGG of 1 to 1.2 gm/kg, 8.6% with IVGG of 1.6 gm/kg, and 4.8% with IVGG of 2 gm/kg (adjusted R-2 = 0.966, p = 0.0017); corresponding prevalence at the convalescent stage was 17.6%, 13.5%, 9.7%, 6.3%, and 3.8%, respectively (adjusted R-2 = 0.993, p = 0.0602). The prevalence of coronary abnormalities was inversely related to the total dose of IVGG and was independent of the aspirin dose. We conclude that 2 gm/kg IVGG combined with at least 30 to 50 mg/kg per day aspirin provides maximum protection against development of coronary abnormalities after KD.