Background: The long-term effect of balloon mitral valvuloplasty (BMV) on the incidence of atrial fibrillation (AF) in patients with severe mitral stenosis (MS) remains undetermined. Aims: To assess the effect of successful BMV on the incidence of chronic AF in patients with severe MS, compare the results with historical controls, and identify factors associated with AF in such patients. Methods: Retrospective analysis of 382 consecutive patients with severe MS and in sinus rhythm (SR) who underwent successful BMV (post procedure mitral valve area (MVA) 1.5 cm 2 , mitral regurgitation (MR) 2/4) at our hospital and followed-up for 1-15.6 (mean 5.6 6 3.9) years with clinical and echocardiographic examination. Results: Thirty-four (8.9%) patients developed AF at follow-up (group A) and 348 patients (group B) remained in SR. At baseline, and in comparison with group B, patients who developed AF (group A) were older, had higher mitral echo score but equal MVA and left atrial (LA) size. The postprocedure MVA was smaller in group A (1.7 6 0.3 cm 2 ) than in group B (2.0 6 0.2 cm 2; P 5 0.002). At follow-up, and in comparison to group B, group A had smaller MVA (1.5 6 0.4 cm 2 vs 1.8 6 0.4 cm 2 P <0.0001), larger LA dimension (49.4 6 6.5 vs 42 6 6.5 mm; P < 0.0001) and higher restenosis rate (35% vs 14%; P 5 0.001). Multivariate logistic regression analysis identified age at follow-up (P < 0.0001), LA size at follow-up (P 5 0.004), and MVA at follow-up (P 5 0.006) as predictors of AF. Conclusions: This study demonstrated favorable effect of BMV on the incidence of AF (8.9%) in patients with severe MS in comparison with reported series (29%) of patients with severe MS with similar baseline characteristics who were not submitted to any intervention. The predictors of AF were age, larger LA, and smaller MVA, at follow-up.