The natural history of aortic stenosis is well defined. There is overwhelming evidence that patients with this disease who develop symptoms require prompt aortic valve replacement, as average survival rapidly falls. Once surgery has been performed age-corrected rates of survival approach the rate in the normal population. Conversely, asymptomatic patients with severe aortic stenosis have an excellent clinical prognosis. Nevertheless, there is a low risk of sudden death or rapid rate of progression to the symptomatic state. This low risk while patients remain asymptomatic does not outweigh the risk associated with valve replacement surgery or the complications of artificial prostheses, so surgery is not recommended for the entire group of asymptomatic patients. Therefore, therapeutic decisions in patients with aortic stenosis are based on the definition of symptomatic status and of hemodynamic severity, so accurate evaluation of these two issues is mandatory. However, establishing symptomatic status and severity of valve disease can be challenging because assessment of subjective symptoms and functional capacity is sometimes ambiguous, particularly in the elderly. Furthermore, it is well recognized that assessment of hemodynamic obstruction defined by echocardiographic indexes such as transvalvular pressure gradient and aortic valve area, is suboptimal because of technical difficulties and poor correlation with symptoms. Hence, aortic stenosis evaluation should be also performed introducing in clinical practice new simple indexes, such as function- and pressure-corrected indexes and energy loss index, that could provide a different estimate of disease severity, based on prognostic indication of adverse clinical outcome. Indeed, clinical outcome represents the real endpoint for defining severity and should be incorporated in clinical assessment and used to aid patient management in unclear situations. The development of heart failure in patients with aortic stenosis is associated with a high mortality rate and requires a careful management that includes an initial evaluation of the severity of the stenosis and the functional state of the left ventricle. Left ventricular dysfunction is usually due to afterload mismatch, but as end stage develops, decline in the intrinsic myocardial contractility becomes the most relevant mechanism. However, separating the effect of myocardial contractile dysfunction from that of afterload mismatch on pump performance is difficult. Dobutamine echocardiography can be useful both by testing myocardial contractile reserve and by separating true from relative aortic stenosis. Unfortunately the optimal management of patients with severe aortic stenosis and left ventricular dysfunction remains controversial, and we still have missing data to determine which patients are more likely to benefit from aortic valve replacement, by improving survival and functional status, with an acceptable perioperative mortality rate.