Retrograde nontransseptal balloon mitral valvuloplasty, a method developed in our institution for the treatment of symptomatic mitral stenosis, avoids transseptal catheterization. Until recently, the self-positioning Inoue balloon catheter, unlike all other commercially available balloon catheters, had not been employed in this nontransseptal technique due to the short length of its catheter shaft. To employ a self-positioning balloon in retrograde nontransseptal balloon mitral valvuloplasty, we modified the Inoue device by extension of the catheter shaft. After retrograde nontransseptal left atrial catheterization using a steerable cardiac catheter, the modified Inoue balloon catheter was inserted through the femoral artery and advanced to the mitral valve retrogradely. Valvuloplasty was performed in 20 patients, with a successful result achieved in all. The modified Inoue balloon catheter was easy to use in retrograde nontransseptal balloon mitral valvuloplasty and showed excellent stability during inflation. Mean mitral valve area increased from 1.0 +/- 0.29 to 2.23 +/- 0.64 cm2 (P < 0.001) and mean transmitral gradient decreased from 11.4 +/- 6 to 4.3 +/- 2.1 mm Hg (P < 0.001). No major or minor complications were observed. Retrograde nontransseptal balloon mitral valvuloplasty using a modified Inoue balloon catheter is a feasible and effective technique for the treatment of symptomatic mitral stenosis. It appears to combine the advantages of avoiding transseptal catheterization with the advantages of this balloon's special configuration.