Immediate outcome and 4-year follow-up results of percutaneous mitral balloon valvotomy (PMV) in patients with previous surgical mitral commissurotomy are studied. Repeat surgical mitral commissurotomy in patients with previous surgical commissurotomy is associated with higher mortality and morbidity. PMV has been proven to be safe and could be an ideal alternative in this patient group. The results of 68 patients with previous surgical commissurotomy were compared with those of 261 patients without prior surgical intervention. A good outcome, defined as the final mitral valve area > 1.5 cm2, was obtained in 51% of the patients with prior surgical commissurotomy compared with 71% in the control group (p = 0.002). During the 4-year follow-up period, there were more patients who required mitral valve replacement (19% vs 7%; p = 0.004) and who were in New York Heart Association functional class III and IV (85% vs 71%; p = 0.02) among those with prior surgical commissurotomy. However, when these patients were divided according to echocardiographic score, those with a score < or = 8 had immediate outcome and long-term results similar to those without prior commissurotomy. PMV can be performed safely in patients with prior surgical commissurotomy. Although results of long-term follow-up in these patients is not as good as those in patients without prior surgical commissurotomy, those with a low echocardiographic score had similar excellent long-term results.