Left atrial (LA) size is known to increase with persistently increased left ventricular (LV) filling pressure. We therefore hypothesized that LA volume might reflect the severity of aortic valve stenosis (AS). Transthoracic echocardiography was performed in 1,758 patients with asymptomatic AS (transaortic Doppler velocity > or =2.5 and < or =4 m/s) in the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) study. LA volume was measured in end-systole in the apical 4-chamber view in 1,503 patients (85%), and aortic valve area (AVA) was estimated by the continuity equation and indexed by body surface area. Mean values for age and AVA were 67 +/- 10 years and 1.27 +/- 0.5 cm2, respectively, and 574 were women (38%). Mean value for LA volume indexed (LAVI) was 36 +/- 13 ml/m2. Enlargement of LA volume (> or =32 ml/m2) was found in 57% of patients. AVA indexed was significantly correlated to LAVI (r = -0.1, p = 0.0002). Multivariate analysis showed that LAVI was significantly related to AVA indexed (beta = -4.1, p = 0.007) in a model that also included mitral regurgitation (beta = 2.8, p <0.0001), history of hypertension (beta = 2.2, p = 0.002), LV end-diastolic volume (beta = 0.05, p <0.0001), presence of LV hypertrophy (beta = 3.4, p <0.0001), and restrictive LV filling pattern (beta = 3.5, p = 0.01). Gender and LV ejection fraction were eliminated from the final model. In conclusion, LA volume is often enlarged in asymptomatic patients with AS. Furthermore, LA volume is related to AVA even when adjusting for other known risk factors for increased LA volume including of measurements of diastolic function.