Thirty six adults with severe mitral stenosis underwent attempted percutaneous mitral commissurotomy. The valvuloplasty could not be performed in 6 cases; post-transseptal haemopericardium (1 case), inability to cross the mitral valve or the septum (5 cases). Therefore percutaneous commissurotomy was performed in 30 cases; the average age was 43 +/- 17 years (range 20-79 years). Eight patients had undergone previous valve surgery; 24 patients were very symptomatic (NYHA Classes III or IV). The valvuloplasty was performed with a single balloon in 22 cases and by simultaneous inflation of two balloons in 8 cases. Moderate mitral regurgitation present before the procedure was significantly aggravated in 2 cases leading to secondary surgery. In the other patients percutaneous commissurotomy led to a clear-cut haemodynamic improvement; the transvalvular pressure gradient fell from 15 +/- 4 to 6 +/- 2 mm Hg, p less than 0.01 and mitral valve surface area increased from 1.1 +/- 0.2 to 2.2 +/- 0.4 cm2, p less than .001. The best results were obtained with the double balloon technique in patients with little valve destruction. Percutaneous mitral valvuloplasty is therefore a tempting alternative to closed heart mitral commissurotomy in pure mitral stenosis with pliable valves. Larger series with a longer follow-up are needed to assess the morbidity and long-term results of this technique.