Abstract A case of a 10-month-old infant is reported in whom a diagnosis of aortic insufficiency was already made at the age of 2 days. The cardiac catheterization and angiocardiographic findings strongly suggested the diagnosis of the so-called aortico-left ventricular tunnel. A surgical closure of the tunnel was made. A mediastinal infection involving the anterior aspect of the aorta ended in perforation and rupture of this vessel which resulted in sudden death on the thirteenth postoperative day. An analysis is made of the anatomical findings and special emphasis is put upon the histologic structure of the tunnel wall. A review of relative literature is made and the anatomical and clinical findings of the previously reported cases are carefully considered. A critical study is made upon the varied hypotheses concerning the pathogenesis of this malformation.