In this prospective study, the long-term effect of posterior leaflet extension with glutaraldehyde-preserved autologous pericardium and associated mitral valve commissurotomy was investigated in patients with mixed mitral valve disease of rheumatic origin. Mitral commissurotomy and posterior leaflet extension using a pericardial patch were performed in 25 patients from 1 January 1994 through 31 December 1995 for mixed mitral valve disease. Preoperatively, no patient had chordal rupture or papillary muscle dysfunction. Four patients had left atrial thrombosis. The mean age was 35.7 +/- 15.4 years. Associated procedures were tricuspid annuloplasty in 4 patients, aortic annuloplasty in 3, aortic and tricuspid annuloplasty in 1, and aortic homograft replacement in 1. There were no early deaths. One patient died 2 years after surgery due to noncardiac causes. Mitral valve area increased from 1.53 +/- 0.63 cm2 to 2 +/- 0.33 cm2 (P = 0. 09), and left atrial diameter decreased from 5.8 +/- 1 cm to 4.86 +/- 1.27 cm (P = 0.07) after 6.1 +/- 0.7 years (range, 5.5 to 71 years). Mitral insufficiency was reduced significantly, from grade 2.65 +/- 0.9 to grade 1.2 +/- 0.9 (P = 0.007). Functional capacity improved in all patients (New York Heart Association functional class, 3 +/- 0.58 preoperatively vs 1.44 +/- 0.82 postoperatively; P = 0.001). Three patients required reoperation and valve replacement. This type of reconstruction may be a good alternative for patients who are not able to use anticoagulant therapy. Long-term results of this technique are acceptable; however, the risk of reoperation is an important disadvantage in these young patients.