The purpose of the present report was to determine the frequency of a congenitally bicuspid aortic valve in patients ≥80 years of age old with aortic stenosis (AS) severe enough to warrant aortic valve replacement. Transcatheter aortic valve implantation (TAVI) has traditionally been reserved for patients ≥80 years of age with severe AS involving a 3-cuspid aortic valve. Traditionally, AS involving a 2-cuspid aortic valve has been a contraindication to TAVI. We examined operatively excised stenotic aortic valves in 364 patients aged ≥80 years to determine the frequency of an underlying congenitally bicuspid aortic valve. Of the 347 octogenarians and 17 nonagenarians, 78 (22%) and 3 (18%) had stenotic congenitally bicuspid aortic valves, respectively. In conclusion, because the results of TAVI are less favorable in patients with stenotic congenitally bicuspid valves than in patients with stenotic tricuspid aortic valves, proper identification of the underlying aortic valve structure is important when considering TAVI as a therapeutic procedure for AS in older patients.