Thirteen children (age range 6 h-11 years, median 4 months) operated upon for aortico-left ventricular tunnel since 1971 are reported. All patients had systolic and diastolic murmurs, 4 of 5 neonates were in severe congestive heart failure. Twelve children had left ventricular hypertrophy on ECG with an ischaemic pattern in the neonates. Chest X-ray revealed cardiomegaly with a broad upper mediastinal shadow from the enlarged aorta. Echocardiography (2DE) revealed a tubular communication between the aorta and the left ventricle bypassing the aortic valve and massive regurgitation through this tunnel demonstrated by Doppler sonography. In 8 patients, the diagnosis was confirmed by angiography. The tunnel arose from the right coronary sinus in 12 and from the left coronary sinus in 1 patient. The tunnel was closed at both ends in 8, at the aortic end only in 3 and at the ventricular end in the remaining 2 cases. One 6-day-old infant, operated upon in 1971 died postoperatively. There was 1 non-cardiac related late death due to a brain tumour. Echocardiographic analysis of left ventricular size and function was carried out in 9 children up to 39 months after surgery. Mild to moderate aortic incompetence was detected during the follow-up period in 2 of 12 patients. All surviving children are leading normal lives.