The first 71 patients with rheumatic mitral stenosis who successfully underwent single rubber-nylon balloon (Inoue balloon) percutaneous mitral valvuloplasty (PMV) from November 1985 to August 1988 had a mean follow-up period of 27.1 +/- 11.6 months (range, 14 to 48 months). Functional status before PMV was New York Heart Association (NYHA) functional class IV in two, class III in 38, and class II in 31. Pre and post PMV and follow-up mean diastolic mitral gradient by catheter method was 17.5 +/- 6.9, 2.7 +/- 3.5, and 3.3 +/- 3.4 mm Hg (p less than 0.001 pre versus post PMV and pre PMV versus follow-up; and p greater than 0.005 post PMV versus follow-up). By Doppler method the mean diastolic gradient was 17.4 +/- 5.5, 8.5 +/- 4.7, and 9.2 +/- 4.1 mm Hg, respectively (p less than 0.001 pre versus post PMV and pre PMV versus follow-up; and p greater than 0.05 post PMV versus follow-up). Mitral valve area was 1.12 +/- 0.26, 2.04 +/- 0.41, and 1.92 +/- 0.45 cm2, respectively (p greater than 0.001 pre versus post PMV and pre PMV versus follow-up; and p less than 0.05 post PMV versus follow-up). The phonocardiographic and vectorcardiographic studies and cardiopulmonary exercise testing showed significant improvement after PMV and at follow-up. At follow-up the NYHA functional class was 1 in 57 patients, class II in 13, and class III in one patient with severe mitral valve calcification and subvalvular fusion, in whom restenosis occurred 18 months after PMV.(ABSTRACT TRUNCATED AT 250 WORDS)