Background: It is well established that hypercholesterolemia can cause endothelial dysfunction. However there is lack of data in humans concerning the relationship between high density lipoprotein cholesterol and endothelial dysfunction. Methods: This study consisted of 756 patients(pts, Male 368, mean Age 54.7짹12.4 years) without significant coronary artery disease underwent acetylcholine (Ach) provocation test by injecting incremental doses of 20, 50 and 100 關g to left coronary artery. Significant cononray artery spasm (CAS) was defined as focal or diffuse severe transient luminal narrowing (>70%) with/without chest pain or ST-T change of EKG. Results: Conventional risk factors of coronary atherosclerosis including age, DM, hypertension were shown in Table. There were statistically significant differences in age, sex, smoking and the HDL level between the two groups. However, muiltiple logistic regression analysis failed to show the significant correlation between the smoking, HDL level and CAS (P=0.775, P=0.393, respectively). Conclusion: Lipid profile including HDL dose not appear to be an independent risk factor for significant CAS but only age and sex were associated with significant CAS (RR=1.03, 1.77 respectively).