The anomalous origin of the right coronary artery is a common finding. With its origin in the left coronary sinus, the right coronary artery can have a route between the aorta and pulmonary artery trunk and can cause myocardial ischemia and sudden death. The anomalous origin of the artery and its route may be diagnosed by coronary angiography or multislice computed tomography. Intravascular ultrasound provides high-resolution images and a precise evaluation of coronary anomalies. The role of intravascular ultrasound was recently demonstrated in the diagnosis of extrinsic compression of the anomalous right coronary artery. We describe 3 cases of anomalous right coronary artery originating in the left coronary sinus. The intravascular ultrasound detected a reduction of the coronary lumen from anomalous course, even when the luminal reduction was not evident by angiography. We suggest that a pharmacological stress test should be used, with a vasoactive drug that simulates physical effort, to determine the reduction of the arterial lumen.