Optimal time for choosing Aortic Valve Replacement in Aortic Stenosis patients is based on understanding the natural history of the disease and prognostic variables, such as age, symptom status and co-morbid factors. In patients with advanced congestive heart failure, the valvular area and transvalvular gradients, determined by echocardiography and cardiac catheterization studies, have limitations for preoperative evaluation; before surgery the reversibility of this myocardial depression must be identified. At present, there is widespread agreement that valve replacement is indicated for symptomatic severe aortic stenosis regardless of age; however, cardiac surgery remains controversial in asymptomatic patients but with abnormal response to exercise, ventricular tachycardia, valve area lesser than 0.6 cm2, and marked or excessive left ventricular hypertrophy. The presence of moderate or severe valvular calcification, together with a rapid increase in aortic-jet velocity, identifies patients with a very poor prognosis and these patients should be considered for surgery. Finally, the decision to operate a patient must be considered on individual factors and whether quality of life is improved, and not just on operative mortality and morbidity.