Objectives Coronary arterial lesions after Kawasaki disease (KD) may cause coronary endothelial dysfunction as the result of intimal hypertrophy. Our purpose was to assess myocardial flow reserve (MFR) and endothelial function in various myocardial regions after KD by using positron emission tomography. Study design Twenty-seven patients, 17.2 ± 3.2 years of age, who had KD at 1.9 ± 1.4 years, and 12 normal healthy subjects, 26.5 ± 3.4 years of age, were evaluated by means of myocardial blood flow (MBF) with ¹⁵O-water positron emission tomography. MFR was estimated by MBF changes under adenosine triphosphate infusion and endothelial function by MBF changes under cold pressor testing. The left ventricle was divided into three coronary territories. Ten stenotic regions, 20 aneurysmal regions, 30 regressed aneurysmal regions, and 21 regions without coronary arterial lesions were compared with 36 control regions of the normal volunteers. Results MBF at rest was similar in each region. Hyperemic blood flow and MFR in each region after KD was significantly lower than those in the regions of normal volunteers. MBF during cold pressor testing was significantly reduced in each region after KD, as compared with no change in the control regions. Conclusions Our study indicates impaired MFR and endothelial function regardless of coronary artery status after KD. (J Pediatr 2003;142:149-54)