Aortic stenosis is the most common acquired valvular disease in the western countries. An older population results in an increased prevalence of calcific aortic stenosis and this pathology is becoming a more important health problem.It is important that we know the basics of this disease and are updated about developments of its treatment. The aim of my work was to present information about calcific aortic stenosis in order to make a simple, but updated presentation of this disease, aiming towards students and to non-cardiology specialized doctors. The most effective treatment for patients with severe aortic stenosis today is surgery. However, the most seriously ill patients may not be accepted for surgery. Therefore the second aim of this work was to present a new alternative treatment for patients previously regarded to be inoperable, the percutaneous valve replacement. With the collaboration of one of the pioneer of this new technique, Pr Alain Cribier from the University Hospital Charles Nicolle in Rouen, France, the development of the percutaneous valve replacement is presented including the first midterm results.