Since it was introduced, in 1984, as an alternative to surgical commissurotomy, percutaneous balloon mitral commissurotomy has been performed in a large number of patients with mitral valve stenosis, significantly improving the valvular function with a final area of 2 square centimetres. The quality of the result obtained basically depends on valve anatomy. The incidence of complications is globally low, with a mortality of 0.5 to 3 percent, and severe mitral regurgitation in 5 percent of the cases. Left-to-right atrial shunts are detected by oxymetry in 20 percent of the patients, but they subsequently vanish in two-thirds of them. For the moment, only medium-term results are available: when the initial result is good functional improvement is the rule, and the incidence of restenosis is low. Conversely, when the result is insufficient or severe mitral regurgitation develops secondary surgery is usually necessary. Before deciding to perform percutaneous commissurotomy, the contre-indications of this method (left atrial thrombosis, moderate to severe mitral insufficiency) must be excluded. In view of the encouraging results obtained, percutaneous commissurotomy can be advocated as first-line treatment of soft valve mitral stenosis. In patients with calcified valve mitral stenosis, valve replacement remains the principal treatment, percutaneous commissurotomy being reserved for special cases.