To the Editor: Njeim and colleagues1 reported on a patient in whom the common trunk arising from the right coronary sinus gave rise to all coronary arteries that supplied the myocardium. This anomaly is called single coronary artery. The authors stated that, after the large common trunk, a right coronary artery (RCA) coursed along the atrioventricular groove and gave rise to the left circumflex coronary artery (LCx). They also indicated that the right ventricular branch of the RCA arising from the proximal common trunk gave rise to the left anterior descending coronary artery (LAD), which traveled in the interventricular groove. We think that the artery called the right ventricular branch by the authors is the left main coronary artery (LMCA) arising from the common right trunk. It seems that the common trunk arising from the right coronary sinus divides into the RCA and LAD just after the division. The LMCA then divides into the LCx and LAD. The RCA is dominant and turns at the apex. The authors' Figures 1 and 2 show the courses of both arteries very well. We recently published a report about a single coronary artery in a patient who presented with inferior myocardial infarction.2 The LMCA arose from the same ostium of the RCA. The LMCA then followed an unusual course to the left side and divided into the LAD and LCx. The LCx was occluded just after the division. We performed primary percutaneous coronary intervention with use of a Judkins left 3.5 guiding catheter. Single coronary artery has been diagnosed in only 0.3% to 1.3% of patients who have undergone coronary angiography.3 When the anomaly presents with acute myocardial infarction, cannulating the ostium and performing percutaneous coronary intervention is difficult. Successful intervention necessitates appropriate catheter selection and skill on the part of the operator.