The results of percutaneous mitral commissurotomy (PMC) were assessed in a series of 600 patients (pts) with mitral stenosis. Their mean age was 43 +/- 15 years (13-86). One hundred and eight had had a previous surgical commissurotomy; 464 were in NYHA class III or IV; atrial fibrillation was present in 188. One hundred and fifty-nine had valvular calcification and angiography disclosed a mild regurgitation (MR) (1/4) in 255. Technical failure occurred in 19 pts. In the remainder, PMC improved valve function: valve area (VA) increased from 1.1 +/- 0.3 cm2 to 2.2 +/- 0.5 cm2 (P less than 0.0001) as assessed by haemodynamics, and from 1 +/- 0.2 to 2 +/- 0.4 cm2 (P less than 0.0001) as assessed by two-dimensional echocardiography. Complications were as follows: death (0.5%), haemopericardium (0.8%), severe MR (3.8%), embolism (3.3%), atrial shunt (14%). Secondary surgery for complications following PMC was necessary in 4.8% of cases. There were poor results (VA less than 1.5 cm2 and/or MR greater than 2/4) in 13%; their predictors being valve anatomy (P less than 0.001), initial valve area (P less than 0.01) and previous surgical commissurotomy (P less than 0.05). Among the 437 pts resident in France, 98% were followed-up 15 +/- 11 months after PMC (range 1-48). After 42 months, the actuarial rates of survival, freedom from need for reoperation and good functional results were respectively: 87 +/- 6%, 81 +/- 3% and 72 +/- 6%.(ABSTRACT TRUNCATED AT 250 WORDS)