Current guidelines recommend that clinical surveillance for patients with moderate aortic stenosis (AS) and aortic valve replacement (AVR) may be considered if there is an indication for coronary revascularization. Recent observational studies, however, have shown that moderate AS is associated with an increased risk of cardiovascular events and mortality. Whether the increased risk of adverse events is caused by associated comorbidities, or to the underlying moderate AS itself, is incompletely understood. Similarly, which patients with moderate AS need close follow-up or could potentially benefit from early AVR is also unknown. In this review, the authors provide a comprehensive overview of the current published reports on moderate AS. They first provide an algorithm that helps to diagnose moderate AS correctly, especially when discordant grading is observed. Although the traditional focus of AS assessment has been on the valve, it is increasingly acknowledged that AS is not only a disease of the aortic valve but also of the ventricle. The authors therefore discuss how multimodality imaging can help to evaluate the left ventricular remodeling response and improve risk stratification in patients with moderate AS. Finally, they summarize current evidence on the management of moderate AS and highlight ongoing trials on AVR in moderate AS.