The present study compares the outcome of percutaneous Inoue-balloon mitral valvuloplasty performed in 21 patients with (group A) and 83 patients without (group B) preexisting moderate mitral regurgitation, using our height-derived balloon-sizing method. All procedures were successfully completed without untoward complications. The immediate increments in mitral valve area measured by echocardiographic methods and optimal valvuloplasty results were significantly higher in group B compared with group A (0.9 cm2 vs. 0.7 cm2, P = 0.01, and 99% vs. 90%, P = 0.007, respectively). No patients in either group sustained a final grade > or = 3/4 angiographic mitral regurgitation. A mild increase in mitral regurgitation was encountered more commonly in group B than in group A patients (22% vs. 0%, P = 0.03). At a mean follow-up of 19-20 months, the substantial majority of patients (> or = 90%) in both groups continued to experience maintained symptomatic benefits. In conclusion, our preliminary data seem to indicate that percutaneous Inoue-balloon mitral valvuloplasty using our height-derived balloon-sizing method in the stepwise dilatation approach in selected patients with significant mitral stenosis and concomitant moderate mitral regurgitation is associated with a low risk of developing severe mitral regurgitation, with effective mitral valve enlargement, and with sustained midterm symptomatic benefits.