Background Moderate aortic stenosis ( MAS ) has not been extensively studied and characterized, as no published study has been specifically devoted to this condition. Methods and Results We aimed to describe the characteristics of patients with MAS and to evaluate their long-term survival compared with that of the general population. This study included 508 patients (mean±SD age, 75±11 years) with MAS (aortic valve area between 1 and 1.5 cm; mean±SD aortic valve area, 1.2±0.15 cm) and preserved left ventricular ejection fraction. Patients were mostly (86.4%) asymptomatic or minimally symptomatic, 78.3% had hypertension, 36.2% were diabetics, and 48.3% had dyslipidemia. Each patient with MAS was matched for the average survival (per year) of all patients of the same age and same sex from our region (Somme department, north of France). During follow-up (median 47 months), 113 patients (22.2%) underwent aortic valve replacement for severe AS. The mean±SD time between inclusion and surgery was 37±22 months. During follow-up, 255 patients (50.2%) died. The 6-year survival of patients with MAS was lower than the expected survival (53±2% versus 65%). In multivariate analysis, age (hazard ratio, 1.04 [95% CI, 1.02-1.05]; P<0.001), prior atrial fibrillation (hazard ratio, 1.35 [95% CI, 1.05-1.73]; P=0.019), and Charlson comorbidity index (hazard ratio, 1.11 [95% CI, 1.05-1.18]; P=0.002) were associated with increased mortality. Aortic valve replacement was associated with better survival (hazard ratio, 0.38 [95% CI, 0.27-0.54]; P<0.001). Conclusions The results of this study show that patients with MAS present many cardiovascular risk factors, a high rate of surgery during follow-up, and increased mortality compared with the general population mainly related to associated comorbidities. Patients with MAS should, therefore, be managed for their cardiovascular risk factors and comorbidities. They require close follow-up, especially when the aortic valve area is close to 1 cm, as aortic valve replacement performed when patients transition to severe AS and develop indications for surgery during follow-up is associated with better survival.