The purpose of this study is to report the long-term follow-up outcome of patients undergoing percutaneous transvenous mitral commissurotomy (PTMC). The follow-up of 68 of 82 (83%) consecutive patients undergoing successful PTMC (mitral valve area of more than 1.5 cm(2) without major complications) in 1987 using the Inoue balloon was analyzed. The mean age at the time of PTMC was 52 +/- 11 years and 81% were female patients. The mean follow-up interval was 98 +/- 37 months (6 to 123). Actuarial survival rate was 98%, 97%, and 86% at 1, 5, and 10 years, respectively; the event-free (death, mitral valve replacement, and repeat PTMC) survival rate was 90%, 85%, and 66% at 1, 5, and 10 years, respectively. According to the echocardiographic findings, patients could be divided into three groups: pliable valve, semipliable valve, and rigid valve. Multivariable analysis identified echocardiographic subgrouping as the major significant predictor of any event: the event-free survival rate being 70% in group 1, 66% in group 2, and 20% in group 3 (P < 0.05). Echocardiographic follow-up was available in 49 of 68 patients (72%); the mitral valve area changed from 1.4 +/- 0.5 before to 2.1 +/- 0.4 immediately post-PTMC, and 1.8 +/- 0.4 cm(2) 10 years after the procedure. The long-term follow-up outcome following successful PTMC was favorable and seems to support it as a viable alternative to surgical commissurotomy in selected patients. Patients with rigid valves should be selected very carefully.