Historical data suggesting poor survival without treatment is largely confined to severe aortic stenosis (AS).To determine the prognostic impact of all levels of native valvular AS.Severity of AS was characterized by convention and by statistical distribution in 122,809 males (61±17 years) and 118,494 females (62±19 years), with measured Aortic Valve (AV) mean gradient, peak velocity and/or area. The relationship between AS severity and survival were then examined during median 1,198 (IQR 591, 2,166) days of follow-up. Patients with previous aortic valve intervention were excluded.Overall, 16,129 (6.7%), 3,315 (1.4%) and 6,383 (2.6%) cases had mild, moderate and severe AS, respectively. On an adjusted basis (versus no AS - 5-year mortality 19%), patients with mild-to-severe AS had an increasing risk of long-term mortality (adjusted hazard ratio 1.44 to 2.09; p<0.001 for all comparisons). 5-year mortality was 43% and 53% in those with moderate AS (mean gradient 20.0 - 39.0 mmHg/peak velocity 3.0 - 3.9 m/s) and severe AS (≥40.0 mmHg, ≥4.0 m/s, or AVA<1.0cm in low-flow, low-gradient severe AS). A markedly increased risk of death from all-causes (5-year mortality >50%) and cardiovascular disease was evident from a mean AV gradient >20.0 mmHg (moderate AS) after adjusting for age, sex, left ventricular systolic, diastolic dysfunction, and aortic regurgitation.These unique data confirm that when left untreated, severe AS is associated with poor long-term survival. Moreover, they also suggest poor survival rates in patients with moderate AS.