We performed percutaneous mitral balloon valvuloplasty (PMV) in 367 patients to compare the effectiveness of PMV between patients with mitral restenosis after surgical commissurotomy (group 1) and patients with unoperated mitral stenosis (group 2). Twenty-two had undergone closed or open mitral commissurotomy 11.2 years before. There were no significant differences in clinical profiles between the two groups. The mitral valve area was increased from 1.0 ± 0.8 to 1.8 ± 0.6 cm² in group 1 and 0.9 ± 0.3 to 2.0 ± 0.7 cm² in group 2 (p> 0.05). The mitral gradient was decreased from 14 ± 5.9 to 6 ± 2.6 mmHg in group 1 and 18 ± 7.0 to 7 ± 5.3 mmHg in group 2 (p> 0.05). The increment of mitral regurgitation and significant left to right shunt after PMV were not significantly different (10% versus 14.7%, 5% versus 10.4% respectively). Optimal results were attained in 75% of the patients in group 1 and in 84.3% of the patients in group 2 (p> 0.05). These results suggest PMV in mitral restenosis after surgical commissurotomy may be safe in selected patients and may be equally effective as in unoperated mitral stenosis.