Between 1975 and 1994, six patients under 15 years old with congenital aortic stenosis underwent relief of left ventricular outflow tract obstruction (LVOTO) by aortoseptal approach. Although we got satisfactory relief of LVOTO in all patients, there were two late deaths. In one patient with residual ventricular septal defect (VSD), intractable ventricular arrhythmia developed 12 years postoperatively. Although the residual VSD closure was performed, the patient died of the arrhythmia. The another one who was the youngest 4-year-old boy suddenly died 4 months postoperatively. The detail about his death was unknown, but we presumed ischemic heart attack as the cause of his death. In 3 of remaining survived 4 patients, we encountered a few complications. They were right ventricular outflow obstruction, coronary artery injury and conduction system injury. All complications and problems we encountered in this series were related to the incision and the reconstruction of aortoseptal approach. In conclusion, the aortoseptal approach is effective technique for relief of LVOTO, but on the other hand it is invasive and not so safe operation. So we should be cautious about these complications and problems.