Single coronary artery arising from the right sinus of Valsalva is a rare congenital coronary anomaly. We report the case of a 77- year- old man who was referred for invasive coronary angiography with a diagnosis of a non-ST-segment elevation acute coronary syndrome of inferior-lateral location. Significant lesion was detected in the proximal segment of the right coronary artery (RCA). During the procedure, it was impossible to catheterize the left coronary ostium, being the left anterior descending filled from the RCA. Given the suspicion of agenesis of the left main, 64-multidetector computed tomography was performed which confirmed the existence of a solitary coronary ostium with a single artery arising from the right sinus of Valsalva.