Myocardial blood flow (MBF) was investigated in children (14.2 +/- 5.01 years) with "resolved" coronary involvement after the onset of Kawasaki disease and angiographically normal epicardial coronary arteries. Ten asymptomatic children with a history of Kawasaki disease had electrocardiography, echocardiography, and positron emission tomography (PET) 10.3 +/- 6.01 years after onset of the acute illness. Myocardial perfusion was assessed by NH(3)- PET at rest and after vasodilatation and compared with that of 10 healthy volunteers (26.1 +/- 6.3 years). No patient had signs of myocardial ischemia; on echocardiography ventricular function was normal without dyskinetic areas or signs of enlargement or stenosis of the proximal coronary arteries. There was no statistical significant difference between patients and volunteers in MBF at rest (0.86 +/- 0.27 vs 0.77 +/- 0.17 ml/g/min), whereas MBF after vasodilatation (2.42 +/- 0.81 vs 3.10 +/- 0.8 ml/g/min) and coronary flow reserve (CFR) (2.89 +/- 0.26 vs 4.09 +/- 1.01 mmHg/ml/g/min) were significantly attenuated in the Kawasaki group. No stress-induced perfusion defects could be detected. In children with a history of Kawasaki disease and angiographically normal epicardial coronary arteries, there is a significant attenuation of MBF after vasodilatation and a significant reduction of CFR. Impairment of vasoreactive ability may indicate residual damage of the coronary arteries and may be a risk factor for atherosclerosis in adulthood.