A 43-year-old man presented with unstable angina. Coronary angiography revealed a single coronary artery originating from the left sinus of Valsalva, giving rise to a left main stem trifurcating to the left anterior descending artery, left circumflex artery, and an anomalous right coronary artery. The anomalous right coronary artery had a retroaortic course and significant proximal tubular stenosis which was stented. The coronary anomaly and abnormal course was confirmed by transesophageal echocardiography. The patient was symptom-free at one-year follow-up. This anomaly does not predispose to accelerated atherosclerosis, and the premature atherosclerosis in our patient was probably due an unhealthy lifestyle.