From May, 1975 to August, 1986, we experienced 21 patients with ruptured aneurysm of the sinus of Valsalva. 1) Their ages ranged from 15 to 52 years with a mean age of 26.7 years, and 14 patients were male and 7 patients were female. Among 18 cases of which aneurysms occurred on the right sinus of Valsalva, 15 cases (83%) ruptured into the right ventricle, 1 case (6%) ruptured into the right atrium and 2 cases (11%) ruptured into the pulmonary artery. All 3 cases of which aneurysms occurred on the noncoronary sinus ruptured into the right atrium. 2) Clinical symptoms consisted of dyspnea (95%), palpitation (81%), chest pain (43%), orthopnea (33%), cough (14%), hemoptysis (5%), oliguria (5%), and fever (5%). In all patients continuous heart murmur was audible. Hepatomegaly (48%), pulmonary basal rale (14%), and pretibial pitting edema (19%) were also observed. 3) In all patients diagnosis was made with cardiac catheterization and angiography, and confirmed by operation excetpt one case. 4) Among 20 patients who had been performed corrective surgery, ventricular septal defect was observed in 16 patients (85%), aortic insufficiency in 5 patients (25%), pulmonary infundibular stenosis in 1 patient (5%), patent foramen ovale in 1 patient (5%), and tricuspid insufficiency in 1 patient (5%). Ventricular septal defect was observed in all 16 patients whose aneurysms of the right coronary sinus of Valsalva ruptured into the right ventricle and the pulmonary artery. 5) All patients survived operation, and no postoperative complication was found except 1 patient to whom reoperation was performed because of postoperative aortic insufficiency and detachment of the patch closure for ventricular septal defect. There was symptomatic improvement in all patients.