Background: Coronary endothelial dysfunction (CED) and subsequent clinical spasm at the myocardial bridge (MB) segment has been proposed as a risk factor for adverse cardiac events. There is limited data regarding clinical and angiographic characteristics according to CED extent/type whether focal or diffuse in patients (pts) with MB. Methods: A total 247 consecutive patients (pts, 141 men; mean age 57.01짹11.87 years) with MB underwent the Ach provocation test by incremental doses of 20, 50, 100 ug into the left coronary artery were enrolled from March 2004 to April 2009. The pts with MB were divided into two groups according to type of CED. The Ach provocation test results and its associated parameters were compared between the focal CED (n=65 pts) and diffuse CED (n=182 pts). Results The baseline angiographic characteristics were not different between the two groups. During the Ach provocation test, the incidence of ischemic chest pain and ST-T change was not different between the two groups. However, the focal CED type showed higher incidence of moderate to severe CED and associated with more severe narrowing in the MB segment as compared with diffuse CED. However, diffuse CED was more associated with clinically significant diffuse and multivessel CAS (Table). On multivariate logistic analysis, diffuse CED were significantly associated with multivessel CAS (p-value < 0.001, OR 0.10, 95%CI 0.25-3.51). Conclusion: In our study, Focal CED was associated with more severe CED and MB milking (angiographic narrowing), whereas Diffuse CED was associated with multivessel CAS, needs clinical implication in pts having MB with endothelial dysfunction.