Coronary arterial fistula was first described by Krause in 1865. Since then more than 200 examples of this lesion have been reported In the literature. It is relatively rare disease and it more commonly originate in the right than in the left coronary artery. A 9-year old male was admitted with the chief complaint of cardiac murmur and diagnosed as coronary A-V fistula at middle segment of the right coronary artery by cardiac catheterization and aortography. On the operation field, the right coronary artery was markedly dilated as one cm. in diameter from the aorta to the middle segment at acute angle of the right ventricle. Fistula opening was obliterated by one stitch horizontal mattress suture with pledget. Postoperative course was uneventful and discharged without problem.[KTCS 1981;1:91-94]