Background This study was a long-term Doppler echocardiographic assessment of mitral valve repair for anterior mitral leaflet prolapse using expanded polytetrafluoroethylene sutures. Methods Between April 1992 and December 2003, we performed mitral valve repair using expanded polytetrafluoroethylene sutures in 204 patients (mean age, 54.6 years) with severe mitral regurgitation (MR) having anterior mitral leaflet prolapse. The cause of valve disease was degenerative in 181 patients (88.7%). Postoperative serial transthoracic echocardiographic studies were performed in all hospital survivors. Residual MR flow detected by color Doppler echocardiography was classified according to the maximum regurgitant jet area. Results The 30-day mortality of 204 patients was 1.4% (3 deaths). There were 12 late deaths and 14 reoperations in this series. Kaplan-Meier survival and freedom from reoperation at 12 years were 84.6% ± 4.0% and 89.9% ± 2.9%, respectively. Postoperative transthoracic echocardiographic assessment after discharge (mean follow-up, 4.2 ± 3.0 years) showed less than mild regurgitation (maximum regurgitant jet area < 4.0 cm 2) in 80.9% of the patients. Overall, freedom from severe MR (maximum regurgitant jet area ≥ 7.0 cm 2) estimates at 12 years were 88.1% ± 3.1%. Freedom from severe MR at 12 years for 114 patients with no MR (maximum regurgitant jet area = 0 cm 2) on intraoperative transesophageal echocardiography and 77 patients with MR was 95.3% ± 2.1% and 82.9% ± 5.1%, respectively ( p = 0.033). Conclusions Twelve-year echocardiographic follow-up demonstrates good long-term results of chordal replacement with expanded polytetrafluoroethylene sutures for anterior mitral leaflet prolapse. To avoid recurrence of regurgitation, a significantly high level of competence of the valve is essential in the repair of anterior mitral leaflet prolapse.