Among all the congenital coronary anomalies, an anomalous origin of the left coronary artery (LCA) from the right sinus of Valsalva is rare. A 48-year-old male patient suffering with lateral acute myocardial infarction was re- ferred for primary percutaneous coronary intervention. The initial angiogram failed to show the LCA, which origi- nated from the right coronary sinus. A critical stenotic lesion was observed in the distal left circumflex artery. The lesion was treated successfully with stenting. We report here on a case of an anomalous origin of the left coronary artery from the right sinus of Valsalva, and the patient presented as acute myocardial infarction. He was successfully treated with primary percutaneous intervention. (Korean Circulation J 2006;36:817-819)