The aim of this study was to assess the real usefulness of percutaneous mitral balloon valvuloplasty (PMV). Eighty patients aged less than 56 years old, with symptomatic pure mitral stenosis, with an hemodynamic and echocardiographic area < 1.5 cm2, without associated valvular or coronary lesions and without surgical contraindications were studied. These were randomized in two groups of similar age, sex, symptomatology, cardiac rhythm, severity of stenosis and valve anatomy, that were subjected to PMV (n = 38) using a double balloon technique or to mitral commissurotomy (n = 42) with extracorporeal circulation (MC). Mitral areas (calculated using modified Gorlin's formula) increased in 1.15 +/- 0.28 and 1.72 +/- 0.34 cm2 in patients subjected to PMV and MC respectively. No patient died, there was one technical failure with PMV and two patients subjected to MC had a surgical wound infection. Mitral regurgitation increased in more than one degree in two patients treated with PMV (5%) and in 6 patients treated with MC (15%). It is concluded that PMV and MC are highly effective and safe procedures for the treatment of mitral stenosis. Mitral areas obtained with MC are higher than with PMV, however a significant improvement of the disease is achieved with both procedures and MC produces mitral regurgitation with a higher frequency.