Abstract: AIM To study the relationship between coronary slow flow (CSF) and endothelial disorder. METHODS Sixty CSF patients confirmed by coronary angiography (CAG) and determined by corrected TIMI frame count (CTFC) method and 20 patients with normal coronary angiography were assigned, respectively, to CSF group and control group (CNF group). Brachial artery diameter, brachial artery endothelium-dependent blood flow-mediated dilation response (FMD) and nitroglycerin-mediated nonendothelium-dependent relaxation response (NID) were measured by high-resolution Doppler ultrasound. Gender, age, body mass index (BMI), smoking rate, blood lipids, fasting blood glucose, blood pressure and endothelial function indicators were compared between groups. RESULTS No significant differences were found in age, BMI, fasting blood sugar, TC, TG, LDL-C, HDL-C, and diastolic blood pressure between groups. The proportion of smoking (63% vs. 25%) and systolic blood pressure ［(126±12) mmHg vs.(119±13) mmHg］ in CSF group was higher than those in the CNF group (P<0.05). The proportion of males in the CSF group was significantly higher than in the CNF group (78% vs. 30%, P<0.01). No significant differences in D0 and NID were found between groups. FMD in the CSF group was significantly lower than in control group ［(6.28±1.30)% vs.(10.2±1.9)%, P<0.01］ and the frame count of CSF group was negatively correlated with FMD (Pearson correlation coefficient, r=-0.70, P<0.01). CONCLUSION CSF is related to endothelial disorder, but other risk factors should also be taken into consideration.