Background and aim: Previous studies suggest the endothelium dependent coronary vasodilation is impaired in patients with microvascular angina. However, Relation between peripheral vascular endothelial function and coronary flow reserve(CFR) in patients with chest pain and normal coronary angiogram remains elusive. Methods:In 32 subjects (mean age=58짹9 yrs, M:F=9:23) with chest pain and normal coronary angiogram, flow mediated dilation(FMD) was assessed in the brachial artery by measuring the change in brachial artery diameter in response to hyperemic flow. In all subjects, the intima-media thickness (IMT) of the common carotid artery using 15 MHz linear array transducer was also measured. Subjects were divided into 2 groups according to CFR ��� 2.0 or > 2.0 and % FMD and IMT was compared with CFR using transthoracic Doppler echocardiography and dipyridamole in distal left anterior descending coronary artery. Results: 1. % FMD was 6.04 짹5.78 % in CFR ���2.0 and 11.77 짹6.82 in CFR > 2.0.(p<0.05) 2. CFR was closely related to peripheral FMD(r= 0.361, p<0.05). 3. IMT was 0.71 짹0.26 in CFR ���2.0 and 0.68 짹 0.14 in CFR >2.0(p=NS). 4. % FMD was not related to IMT(p=NS). Conclusion: Above findings suggest that FMD of brachial artery reflects CFR and impaired CFR in microvascular angina is primarily related to vascular endothelial dysfunction rather than IMT itself.