The long-term results of percutaneous mitral commissurotomy were evaluated in 606 patients with a mean age of 48 +/- 14 years. One hundred and eleven patients (48%) had a history of surgical commissurotomy. At echocardiography, 91 patients (15%) had flexible leaflets and little subvalvular apparatus, and 180 (30%) have calcified valves. The procedure was performed with a single balloon in 21 patients, a double balloon in 402 patients and Inoue's balloon in 183 patients. A good immediate, result, defined as a mitral valve surface area > or = 1.5 cm2 without > 2/4 mitral regurgitation, was obtained in 528 patients (87%). Five hundred and eighty patients (96%) were followed up for an average of 30 +/- 18 months. The actuarial 5 year rates were: survival 94 +/- 4%; survival without surgery 74 +/- 6%; survival without surgery with a good functional result (NYHA Classe I and II) 66% +/- 6%. Factors predictive of a good functional result were the valvular anatomy (p = 0.01), the NYHA Class before the procedure (p = 0.02), the cardiothoracic ratio before the procedure (p = 0.005) and mitral valve surface area after the procedure (p = 0.007). The type of balloon had no influence on the result (p = 0.54). The authors conclude that the 5 year results of percutaneous mitral commissurotomy are good in a population of patients with varied characteristics. The persistence of good functional results depends on anatomical and functional data and the quality of the initial result, but not on variables related to the procedure.