Aortic valve area (AVA) of 1.0 cm2 and/or mean transaortic pressure gradient (MPG) of >40 mm Hg and/or peak aortic jet velocity (Vmax) of >4 m/s are presently used to characterize severe aortic stenosis (AS). AVA Using these criteria, the average AVA is 0.6 cm2 and the prevalence of severe AS is 25%. However, there is considerable overlap in AVA between patients with and those without severe AS. Thus, it can be anticipated that many patients with mild or moderate AS will undergo aortic valve replacement because of symptoms or risk factors such as older age, higher MPG, and reduced left ventricular systolic function. This article focuses on identifying patients with severe AS. Symptoms of severe AS include chest pain due to angina pectoris caused by increased cardiac work or heart failure due to decreased cardiac work. Asymptomatic patients with severe AS may have increased mortality rates compared with asymptomatic patients with mild or moderate AS. The presence of additional risk factors for adverse outcomes including older age, lower ejection fraction, and higher MPG further defines patients with severe AS. These patients should be identified prior to surgery so that appropriate precautions can be taken during anesthesia and surgery. Treatment for severe AS includes medical management with beta-blockers and calcium channel blockers and surgical aortic valve replacement.