We reviewed certain clinical and morphologic findings in 9 patients who had aortic valve replacement (AVR) for aortic stenosis (AS) when ≥90 years of age. All had AVR from February 2000 to April 2006. The aortic valve areas ranged from 0.41 to 1.00 cm², and the transvalvular peak systolic gradients ranged from 20 to 110 mm Hg. The left ventricular ejection fractions were ≥50% in 6 of the 9 patients. The aortic valve was congenitally bicuspid in 3 patients, and the operatively excised valves in them weighed 4.20, 5.73, and 9.75 g, respectively (mean 6.56). The other 6 patients had 3-cuspid valves without commissural fusion, and the operatively excised valves in them weighed 0.43, 0.94, 1.08, 1.51, 1.98, and 4.43 g, respectively (median 1.30, mean 1.73). Coronary artery bypass grafting (CABG) was performed at the time of AVR in 8 of the patients. One patient died a day postoperatively and 2 others died 874 and 1,011 days, respectively, after operation. Two were in skilled nursing units postoperatively for several weeks. In conclusion, AS can be severe in nonagenarians and may be superimposed on a congenitally bicuspid aortic valve.