The boy was first admitted to the Department of Pediatric Cardiology at the age of 4 1/2 because of cardiac murmur diagnosed on the third day of life. A diastolic murmur of a grade 4/6, left ventricular hypertrophy as well as left aortal and ventricular dilatation were discovered. The findings showed a tendency of increase with time, but the patient had no symptoms. X-ray in the long axis view revealed a defect within the upper part of the interventricular septum immediately below the aorta, and dilated right coronary sinus. An invasive diagnostic method was undertaken, as well. The operative procedure was done with a total cardio-pulmonary bypass and hypothermia (29 degrees C). A tunnel from the anterior aortal wall through the outflow tract of the right ventricle to the left side of the heart was established intraoperatively. The defect was solved by a "sandwich" technique (two patch technique). Postoperative period was uneventful. A Doppler echocardiogram demonstrated the normal hemodynamic status of the patient without the left-to-right or right-to-left shunt and aortal insufficiency.