ALVT is a very rare congenital malformation. Until 1983 a collective review reported only 37 cases published. A 5-month-old girl with a body weight of 5.5 kg was referred for cardiomegaly and cardiac murmur. 2D-echo revealed the diagnosis which was later confirmed by angiography. The child was then operated upon with extracorporeal circulation using deep hypothermia (20 degrees C). The aortic orifice of the tunnel was closed with 3 pledget reinforced sutures. Cross-clamp time was 17 min. Electromagnetic flowmetry suggested an insufficiency of 78% preoperatively, and postoperatively this was reduced to 6%. Angiography was performed two weeks postoperatively, revealing mild valvular aortic insufficiency. She was discharged from the hospital 15 days postoperatively. ALVT should be corrected surgically as soon as the diagnosis is made.