Background: Spastic coronary artery on baseline coronary angiogram reflects the disruption of balanced coronary vasomotor tone and may be associated with clinically significant vasospasm. We investigated whether the spastic coronary arteries at baseline coronary angiogram is more vulnerable to the intracoronary acetylcholine (Ach) provocation test compared with the patients (pts) without baseline spasm. Method: A total 1,039 pts (517 men, mean age 56 짹 11.6 years, range 20-82 years) who underwent diagnostic coronary angiography with incremental acetylcholine provocation test were enrolled for the study. Angiographic and clinical parameters of the baseline spasm group (n=394) were compared with those of the no baseline spasm group (n=645). Result: Thirty eight percent of enrolled pts showed positive baseline spasm at baseline coronary angiogram (394/1039). Baseline characteristics were well balanced between the two groups. The baseline spasm group showed higher frequency of significant Ach-induced endothelial dysfunction compared with the no baseline spasm group (odd ratio 2.465, CI 1.902~3.194, P<0.001). Conversely, the relative risk of preexisting baseline spasm is 1.76 (CI 1.490 ~ 2.082, P<0.001) among the pts with positive Ach provocation test. The diameter stenosis measured by quantitative coronary angiography (QCA) during the Ach provocation test in the baseline spasm group was higher than that of he no baseline spasm group (70.1% vs 67.7%, P=0.039); that is more severe Ach-induced endothelial dysfunction was observed in the baseline spasm group. Typical ischemic chest pain and the ST-T change in ECG were more frequently developed in the baseline spasm group during the Ach-provocation test (56.4% vs. 40.3%, P<0.001, 9.52% vs. 5.48%, P=0.016, respectively). Conclusion: Spastic coronary artery on baseline coronary angiogram appears higher chance of more frequent Ach-induced endothelial dysfunction and diffuse significant inducible vasospasm when compared with the pts who has no baseline spasm.