Aneurysm of the sinus of Valsalva is fairly rare. Between 1987 and 1994, we operated on a total of 12 cases of aneurysm of the sinus of Valsalva at the Inje University Seoul Paik Hospital. This represents 0.7% of all cardiac operation under cardiopulmonary bypass. There were eight male and four female patients aged from 8 to 38 years(mean, 19.2 years). 8 of 12 patients had ruptured aneurysms. The origin of aneurysm of the sinus of Valsalva was the right coronary sinus in 10(83. 3%), and the noncoronary sinus in 2(16.6%). In ruptured aneurysm, the origin was the right oronary sinus in 6, and the noncoronary sinus in 2. The aneurysms originating from the right coronary sinus ruptured into the right ventricle in 5, and into both the right atrium and right ventricle in 1. The aneurysms originating from the noncoronary sinus ruptured into the right ventricle in 1, and into the right atrium in 1. Associated congenital cardiac defects included ventricular septal defect in 10(83.3%) patients 39 cases of these were associated with the aneurysms of the right coronary sinus), aortic regurgi- tation in 3 (all of these had an additional ventricular septal defect), mitral regurgitation in 1, and double chambered right ventricle in 1. No hospital deaths occurred, although one late death occurred as a result of endocarditis 15 months after the first operation. The mean follow-up period was 29 months, range from 4 to 60 months. Eleven patients except one late death were in New York Heart Association class 1. Due to the low mortality risk o( an operation for aneur sm of the sinus of Valsalva, a ruptured aneurysm of the sinus of Valsalva should be corrected surgically when the diagnosis is mane, and unruptured aneurysm of the sinus of Valsava with complication should also be operated. In most cases the aorta was opened to examine the morphology of the aneurysm and the aortic cusps, and an associated aortic valve defect should be corrected simultaneously.