Patients with myocardial bridging (MB) may experience myocardial ischemia. Coronary stenting was reported to serve as an effective interventional approach to improve symptoms in selected patients with MB, but is related to high risk of coronary perforation. The aim of this study is to investigate vessel area in the myocardial bridge segment in comparison to that of adjacent segments proximal and distal to MB using intravascular ultrasound. A total of 81 myocardial bridge segments, characterized by a half-moon-shaped echolucent zone surrounding the intramural artery, were found in 78 patients using intravascular ultrasound. The cross-sectional area within the external elastic membrane and minimum and maximum diameters in the myocardial bridge segment and adjacent reference vessel segments were measured. Diastolic cross-sectional area within the external elastic membrane in the myocardial bridge segment was significantly smaller than that in adjacent segments both proximal and distal to MB (5.48+/-2.59 vs 9.40+/-3.48 and 7.22+/-2.87 mm2, respectively, both p<0.001). Maximum vessel diameter in the myocardial bridge segment during diastole was also smaller than that in the segment distal to MB (2.74+/-0.61 vs 3.12+/-0.59 mm, p<0.001). In conclusion, our study showed that vessel area in the myocardial bridge segment was smaller than that in adjacent segments proximal and distal to MB.