The objectives of this study were to assess the effect of percutaneous mitral balloon valvuloplasty (PBMV) on the plasma levels of N-terminal-pro B-type natriuretic peptide (NT-proBNP) in patients with mitral stenosis (MS) and to investigate the relationship between the changes in hemodynamic variables and NT-proBNP levels after PBMV. Plasma NT-proBNP concentrations were obtained from 60 symptomatic patients with rheumatic MS who underwent PBMV, and in 35 age- and gender-matched healthy volunteers. Patients with MS were found to have significantly higher levels of plasma NT-proBNP compared to the control group (293 [77-1093] pg/mL versus 24 [12-67] pg/mL, respectively; [P < 0.001]). The mean preprocedural NT-proBNP level fell significantly from 293 (77-1093) pg/mL to 214 (69-1028) pg/mL (P < 0.001) following PBMV. The percentage decrease in plasma NT- proBNP levels was correlated only with the percentage decrease in systolic pulmonary artery pressure (r = 0.687, P < 0.001) and this correlation persisted in linear regression analysis (beta = -0.013; 95% CI [-0.018- -0.008] and P < 0.001). However, NT-proBNP levels did not correlate with the percentage of improvement in NYHA functional class, mitral valve gradients, or left atrial pressure (all P > 0.05). These findings indicate that NT-proBNP measurement following PBMV may be valuable for evaluating changes in pulmonary artery pressure and that elevated NT- proBNP levels in patients with MS may reflect the increased wall stress in the left atrium and right side of the heart.