Aspergillus species causing endocarditis on a native heart valve is a rare occurrence with an exceedingly high mortality. This report describes a 60-year-old man who developed Aspergillus clavatus endocarditis of the aortic valve 18 months after coronary artery bypass surgery. The aortic valve was angiographically normal on cardiac catheterization performed before coronary artery surgery. Despite aortic valve replacement and amphotericin B therapy, the patient died as a result of Aspergillus species aortitis with occlusion of the coronary ostia and bypass grafts. Coronary artery surgery may be complicated by this highly lethal infection, which is difficult to diagnose and treat.