Eighty patients with tight and pliable mitral stenosis were randomized in a prospective trial comparing percutaneous balloon valvuloplasty and open commissurotomy. Mitral valve area increased significantly in both groups immediately after the procedures. However, a decrease in mitral valve area occurred in both groups at 6, 12 and 24 months during the follow-up. There was no death in either group. Two patients had significant mitral regurgitation after percutaneous balloon valvuloplasty. After 24 months, all patients in the commissurotomy group and 97.4% of the patients in the balloon valvuloplasty group were in New York Heart Association functional class I or II.