A patient with an acute coronary syndrome underwent coronary angiography, which showed only a moderate stenosis in the mid portion of the left anterior descending artery. Intravascular ultrasound was performed for a better assessment of the lesion, and surprisingly, it showed a myocardial bridge over the narrowed segment, which was unapparent at angiography. In fact, the systolic compression of the artery was very limited, and no 'step down-step up' course was recognized. Given the absence of significant atherosclerosis in the intramyocardial and adjacent segments, and considering the poor results reported for stenting of tunnelled coronary arteries, we decided to treat the patient medically. At 6-month follow-up, the patient is asymptomatic and has no inducible ischemia.In conclusion, this case shows how intravascular ultrasound can be useful in patients with an unclear angiographic diagnosis for a better patient management.