The essential issue during preoperative assessment is to estimate the risk/benefit ratio between the risk of noncardiac surgery and the severity of aortic stenosis. However, different definitions of disease severity have been used in published studies, impeding the simple interpretation of those studies. Irrespective of noncardiac surgery, symptomatic patients with severe aortic stenosis, determined according to the definitions published by an American College of Cardiology/American Heart Association task force,21 are at a highly increased risk for experiencing adverse events during follow-up. Even asymptomatic patients with severe aortic stenosis display a 1 to 2% risk of sudden cardiac death, while patients with moderate aortic stenosis display an overall risk that is comparable to that of the general “healthy” population.11,21 On the basis of a variety of data on hemodynamics and natural history, moderate aortic stenosis was defined as an aortic valve area of 1.0 to 1.5 cm2 (mean transvalvular gradient, approximately 25 to 50 mm Hg at normal cardiac output), and severe aortic stenosis was defined as an aortic valve area of < 1.0 cm2. When stenosis is severe and cardiac output is normal, the mean transvalvular gradient is generally > 50 mm Hg.,21The critical reduction of the aortic valve area individually depends on the body height and size of the affected patients, and Doppler echocardiography data should be included for quantification. Asymptomatic patients with a peak transvalvular jet velocity of > 4 m/s have a > 50% likelihood of symptom onset or death within 2 years.22 None of the latter patients with moderately sized aortic stenoses died suddenly. Adverse events were unlikely to develop during follow-up in patients with a jet velocity of < 3 m/s.22 All of those data were derived from observational data of large populations, which do not reflect the perioperative situation of patients with aortic stenosis. Nevertheless, we used the definitions cited above for a clear, traceable risk assessment of adult patients, since these definitions appear to give reliable estimates even for valve-related risk during noncardiac surgery. Operative risk stratification should further include the consequences of severe aortic stenosis, such as left ventricular (LV) hypertrophy and LV dysfunction, and the type of noncardiac surgery.