Two critically ill newborns with aortico-left ventricular tunnel and severe heart failure were operated on at six and 14 hours after birth. The diagnosis was established clinically by the auscultatory finding of systolic and diastolic murmurs and by two-dimensional and Doppler echocardiography. In the first newborn, the left aortic sinus was connected with the left ventricle below the aortic valve by an aneurysmatically dilated tunnel. In the second patient, the tunnel connected the right aortic sinus and the left ventricle. The repair was performed under deep hypothermia, total hemodilution, and cardiopulmonary bypass. The tunnel was closed with two patches of Gore-Tex on the aortic and ventricular orifices. Both children are free from symptoms and are developing normally 10 and 8 months after repair.