Acquired aortic disease is now currently corrected by total prosthetic replacement of the aortic valve. Aortic valve replacement was performed in 13 cases at the Montreal Heart Institute in 1963. In the first four cases, Bahnson aortic leaflets were used; in the remaining nine, the Starr-Edwards semirigid aortic valve prosthesis. The surgical technique employed is described. There were two operative deaths and two late deaths. The results have been excellent in all of the survivors but one. They have returned to full-time activities and four of them to strenuous physical work. It is the contention of the authors that aortic valve replacement is a surgical procedure with acceptable risks, offering hope for a near-normal life to patients crippled by severe aortic valvular lesions.