Background and Objectives竊�The slow coronary flow (SCF) is a common observation characterized by delayed contrast dye opacification without significant stenosis of epicardial coronary artery. However its pathophysiology and clinical implication have not been fully understood. Some reports suggested that SCF might be caused by the atherosclerotic changes of microvascular coronary artery. It is well known that carotid intima-media thickness (IMT) and pulse wave velocity (PWV) are excellent parameters indicating vascular atherosclerosis, so we compared the carotid IMT and PWV between SCF and normal coronary flow (NCF) group. Subjects and Methods竊�We included 76 patients complained of chest pain who showed normal coronary angiogram. TIMI frame count (TFC) was examined in each left and right coronary artery. We statistically defined SCF as if TFC was more than 25. Carotid IMT was measured by recording ultrasonographic images of both the left and the right common carotid artery. PWV was calculated from measurements of the pulse transit time between two recording sites, the femoral and carotid external arteries. Results竊�Eleven patients were included in SCF group and 65 patients were in NCF group. TIMI frame counts of SCF and NCF group were 29.5짹3.9 and 15.7짹4.4, respectively. Cardiovascular risk factors such as age, DM, hypertension, hyperlipidemia were not significantly different between both groups. Interestingly, the SCF group had a significantly larger portion of male patients than that of NCF group (81.8% vs. 46.2%, p<0.05). The carotid IMT of SCF group was significantly different with that of NCF group (0.12짹0.04mm and 0.09짹0.02mm, respectively, p<0.01). However, there was no significant difference in PWV between groups (SCF;14.2짹2.4m/s, NCF;14.4짹2.8m/s, p>0.05). Conclusion竊�This present findings allow us to conclude that SCF in normal angiogram may reflect the early atherosclerotic change of microvasculature before the developments of epicardial coronary artery atherosclerosis and arterial stiffness.