The quadricuspid aortic valve is a rare aortic valve congenital malformation. The 2D transthoracic ultrasound (TTU) is not always effective in diagnosing quadricuspid aortic valves. The aim of this article is to present a case treated in our department, initially diagnosed as a mainly stenotic aortic valvular disease, while reviewing the clinical cases described so far. The authors report the case of a 74 year-old female patient with a mainly stenotic aortic valvular disease diagnosed by TTU. The only known risk factor was arterial hypertension. She underwent elective surgery in June 2005. The surgery consisted in replacing the quadricuspid aortic valve by a Carpentier Perimount no 21 Ao prosthesis. There were no post-operative complications. The patient revealed no symptoms in the post-operative 6 months and 1 year follow-up visits. The quadricupid aortic valve is a rare congenital malformation, with a considerable risk of serious complications. Patients with this diagnosis should be exhaustively studied. Medical literature describes some cases of quadricuspid aortic valve operated in other clinical centres. We present here the only case operated in our department in a 20-years period.