OBJECTIVE Severe aortic regurgitation (AR) is a contraindication for balloon aortic valvuloplasty (BAV). As the effects of mild and moderate AR are unknown, the study aim was to determine the effects of BAV in patients with mild and moderate AR. METHODS A total of 263 consecutive patients with symptomatic severe aortic stenosis (AS) who underwent BAV was included in the study. The patients were stratified into three groups according to their pre-procedural degree of AR, as assessed echocardiographically. RESULTS The study groups included pre-BAV with no AR (n = 76; 28.9%), mild AR (n = 180; 68.4%), and moderate AR (n = 7; 2.7%). There were no differences in the baseline characteristics of the groups, with a mean age of 81.9 +/- 9.0 years and a Society of Thoracic Surgeons score of 12.9 +/- 6.0. Among patients with no AR pre-BAV, 48.7% developed mild AR post-BAV, while 4.5% of those with mild AR pre-BAV developed moderate AR (p < 0.001). The majority of patients (93%) had mild AR both pre- and post-BAV. Only two patients developed severe AR post-BAV. A good agreement existed between the categories of AR pre- and post-BAV (weighted kappa = 0.54, 95% CI, 0.43-0.65). The degree of AR post-BAV did not impact on the mortality rates of mild AR (41.1%), moderate AR (46.9%), or severe AR (63.6%) (p = 0.31). CONCLUSIONS It is safe to perform BAV in patients with mild and moderate AR. About half of all patients with no AR may develop mild AR, the majority will remain in mild AR, and a small percentage will develop moderate or severe AR.