Abstract Acongenitally bicuspid aortic valve may function normally, it may be stenotic with or without associated regurgitation or it may be purely regurgitant (no associated stenosis). 1,2 Such a valve may function normally for many years and then it may become stenotic (as calcific deposits build up) or it may become purely regurgitant (because of superimposed infective endocarditis or because of reasons unclear). Once a bicuspid valve develops some degree of stenosis, its course thereafter is one of gradually worsening stenosis; once a bicuspid valve develops some degree of pure regurgitation (without associated stenosis), its course thereafter is one of gradually worsening regurgitation. Recently, we encountered a man who 8 years earlier had evidence of severe pure aortic regurgitation (no element of stenosis) and thereafter he went on to develop severe aortic valve stenosis with virtual loss of the regurgitation. To our knowledge, conversion from pure aortic regurgitation to severe aortic stenosis has not been reported. This report records such an occurrence.