In patients with severe asymptomatic aortic stenosis (AS), the decision to operate is difficult. In effect, the operative mortality is not negligible (about 5% in subjects age over 75 years) while spontaneous mortality from sudden death is low (about 0.4% per year). The aim of the stress test is to detect patients who are falsely asymptomatic (due to subconscious self limitation of daily physical activity) for whom aortic valvular replacement should be proposed because of the risk of sudden death. On the other hand, if the stress test is negative (normal blood pressure elevation on effort, the absence of either any symptoms, ST segment depression of more than 2 mm, or severe ventricular rhythm disorders linked to effort), surgical intervention could (and probably should) be postponed. This article presents the studies which have allowed integration of the stress test as an aid to the decision of when to operate in patients with asymptomatic severe AS with good left ventricular function into the European and North American recommendations.