Coronary artery fistulae are very rare congenital anomalies which constitute 0.2-0.4% of all congenital heart diseases. The right chambers of the heart are the most frequent communication site of the coronary fistulae and may cause hemodynamic impairment in the coronary circulation. The fistulae arise frequently from right coronary and left anterior descending arteries. Fistulae from left circumflex artery are very rare. We report a case in which transcatheter embolization was performed with 3-mm Guglielmi detachable coils in a young adult with a rare type of congenital fistula originating from the circumflex artery and draining into the coronary sinus. © 2009 Japanese College of Cardiology.