Aortic stenosis is perhaps the most common of all valvular heart diseases in the developed nations of the world. Once primarily caused by rheumatic fever, the most common pathogenesis today is an active inflammatory process with some features that are similar to atherosclerosis. Because of this shift, the age at onset of severe obstruction has changed from the sixth decade 50 years ago to the eighth decade in most individuals today. The onset of symptoms remains a key determinant of outcome, although the later age at onset may make it difficult to discern if aortic stenosis or other age-related comorbidities is the cause of the symptoms. Once symptoms of aortic stenosis develop, life expectancy is shortened to ≈3 years unless the mechanical obstruction to left ventricular outflow is relieved by aortic valve replacement. Traditionally performed during cardiac surgery, aortic valve replacement now may be performed safely and effectively using transcatheter techniques, potentially revolutionizing the approach to this potentially fatal disease.