Subannular aortic aneurysm is a word-wide rare disease entity occurring predominantly in young black men. In Korea, there has been no report. We report one patient, 46 years old man, who had been operated urgently because of acute aortic insufficiency and aortic valvular vegetation after antibiotics treatment of Subacute bacterial endocarditis for 6wks. At the operative field, We found the bulging aneurysmal mass between the aorta and superior vena cava above the right pulmonary artery, which has subannular communicating opening into the left ventricular cavity, beneath the anterior commissure of the bicuspid aortic valve. Pathologic findings are consistent with "portion of vascular wall with features of aneurysm.* The patients survived aortic valve replacement and patch closure of subannular aneurysm, with no symptoms at one-year postoperative follow-up.w-up.