Selective right coronary angiography in a 22-year-old woman demonstrated an enormous right coronary artery, with the contrast medium opacifying to the left coronary artery through a well-developed collateral circulation and draining into the pulmonary artery. The diagnosis of anomalous origin of the left coronary artery from the pulmonary trunk [also known as Bland-White-Garland (BWG) syndrome] was thus established. Magnetic resonance imaging (MRI) showed a dilated right coronary artery arising from the aorta, the left coronary artery from the pulmonary trunk but not from the aorta, and well-developed channels in the interventricular septum. MRI could be a useful tool for diagnosing anomalous origin of the left coronary artery from the pulmonary trunk.