Out of 212 patients undergoing open mitral commissurotomy for mitral stenosis from January, 1972, to December, 1981, 53 patients had extremely severe subvalvular changes. In this study, we evaluated postoperative results in these 53 patients. There were 2 operative deaths (3.8%) and 1 late death (1.9%). Of the 50 surviving patients, 34 (68%) were in New York Heart Association Class I and 13 patients (26%) were in Class II, postoperatively. Three patients (6%) required reoperations an average of 5 years 5 months because of the progression of residual mitral regurgitation. The actuarial rate of freedom from mortality and reoperation was 78.6% at 10 years after operation. When anticoagulant therapy was not given, no patient had thromboembolic complications. Postoperative hemodynamic studies demonstrated that mean diastolic gradients across the mitral valve were 5.30 +/- 1.25 mm Hg (standard deviation) at rest and 9.50 +/- 5.13 mm Hg during exercise. Calculated mitral valve areas were 1.86 +/- 0.48 cm2 at rest and 1.88 +/- 0.51 cm2 during exercise. There was no evidence of any adverse effects of mild to moderate valve calcification. It is concluded that for a follow-up period as long as 10 years, the stenosed mitral valve with greatly advanced subvalvular deformities can be salvaged with low mortality, low incidence of reoperation, and acceptable valve function even when such deformities are associated with mild to moderate calcification.