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 age impact on CED severity in patients (pts) with MB. Methods: A total 622 consecutive patients (pts, Men; 371, 59.6%, mean age 52.9짹 12.0 years) who underwent coronary angiography with acetylcholine (Ach) provocation test were enrolled for this study. Study population was divided according to age limit of fifty years. Results: Regarding baseline characteristics, age group more than 50 years had more hypertension (55.9% vs. 35.0%, p<0.001), diabetes (13.2% vs. 2.7%, p<0.001), and dyslipidemia(26.3% vs. 14.4 %, P<0.001). Ach test clinical endpoints were similar between the two groups. However, in age group more than 50 years; the frequency of significant Ach-induced spasm, response to A2 dose, mulitvessels spasm and >70% narrowing on QCA were significant higher on multivariate analysis (Table). Conclusions: In pts with MB, older age (more than 50 years) was associated with more frequent significant spasm and multivessel spasm as assessed with Ach provocation test. Special care should be emphasized in these patients.