This is a case report of a coronary artery fistula through a mural thrombus on a left ventricular aneurysm into the left ventricle. Serial coronary arteriography disclosed a vessel exhibiting a "smokelike" appearance originating at the anterior descending artery. This abnormal finding faded away over a period of 10 years with a decrease in size of the mural thrombus. This finding strongly suggests that the abnormal vessel represents an acquired neovascularity related to a newly developed thrombus.