Background Brain natriuretic peptide (BNP) level is related to disease severity in aortic stenosis. The aim of this study was to assess the associations between BNP level and disease severity in aortic stenosis. Methods Thirty-seven patients (20male; aged 71짹8.4 years) with isolated aortic stenosis underwent independent assessment of symptoms, transthoracic echocardiography and measurement of plasma levels of BNP. Results Mean pressure gradient was 63짹24 mmHg and mean aortic valve area was 0.67짹0.5 cm2. 9 patients were classified as mild AS (PG mean<30mmHg), 13 patients as moderate AS (PG mean 30-50 mmHg) and 15 patients as severe AS (PG mean>50mmHg). At the study entry, Plasma BNP levels were higher in symptomatic patients than in asymptomatic patients (BNP 352.3짹529 vs 53.2짹43.2 pg/ml, P<0.05). BNP levels increased with NYHA class (BNP 26짹19 class II, 93짹15 class III, 721짹605 class IV). Significant linear correlation BNP levels between transaortic pressure gradients, fractional shortening-velocity ratio (FSVR), ejection fraction-velocity ratio (EFVR) as severity index of AS in echocardiography (r=0.57, r=-0.5 and r=-0.53 ; all P<0.05). BNP was positively correlated with LVMI (r = 0.74, P<0.05) but no correlation was found between BNP and LVEF at resting state. Conclusions Plasma BNP levels are elevated in symptomatic patients with aortic stenosis even though their LV systolic dysfunction were not overt at rest. Furthermore, BNP is closely related to echocardiographic indices reflecting severity of aortic stenosis. This study suggests that measurement of BNP may complement clinical and echocardiographic assessment of aortic stenosis, and could potentially be used to monitor progression of disease non-invasively. These markers may also be useful to identify the optimum time for surgery in AS.