Objective: It is not clear whether flow-mediated brachial arterial dilation (FMD) is associated with lesion characteristics of coronary artery, although it is known to be related with coronary endothelial dysfunction and with adverse cardiovascular events. We assessed the association between FMD and lesion characteristics of coronary artery in patients underwent percutaneous coronary intervention (PCI). Methods: Target lesions of 12 patients (9 men, mean 60 years), who underwent PCI, were analyzed for intravascular ultrasound (IVUS) radiofrequency data using IVUS-virtual histology (VH) software and for FMD using high-resolution ultrasound. Results: FMD of study patients was 3.09짹3.2%. Lesion length, minimal luminal diameter, and plaque burden of the target coronary lesion were 20.2짹3.7mm, 2.2짹0.1mm, and 66.2짹13.6, respectively. Tissue characteristics of the lesion at the narrowest luminal diameter showed 4.3짹3.2mm2 (56.9%) of fibrous area, 1.1짹1.4mm2 (12.5%) of fibrofatty area, 0.5짹0.4mm2 (10.3%) of dense calcified area, and 1.4짹1.1mm2 (20.3%) of necrotic core area. See the table for correlation of IVUS-VH findings with FMD. Conclusions: Brachial arterial endothelial dysfunction is associated with plaque burden, dense calcified, and necrotic core area of the coronary artery plaque in patients underwent PCI. This study suggests that systemic endothelial dysfunction can be a marker of vulnerable plaque and higher plaque burden. The study patients will be enrolled more at presentation.