A multi-leaflet valve adapted to serve as a prosthesis for diseased native valve of a mammal is incorporated in self-expandable or inflatable endovascular stents or stents to form a combination which is introduced on a catheter with a guide wire into the circulatory system of the mammal to replace the diseased native valve. Once the combination is at the desired location the stent is caused to expand and affix itself to the patient's vessel wall. The prosthetic valve has the shape of a truncated cone that has an inflow and an outflow orifice with leaflets forming the outflow orifice and forming a plurality of commissures. A first flexible circular support is affixed in a substantially circular fashion around the truncated cone in proximity of the inflow orifice, and a second flexible circular support is affixed at the location of the commissures to form a circle around the truncated cone in proximity of the outflow orifice. The circular supports maintain the shape of the valve during the surgical implantation procedure and thereafter.