Among 206 consecutive patients having undergone mitral valve repair with a prosthetic ring between 1972 and 1979 in our institution, the 195 patients (94.5%) who survived the operation were studied to assess the long-term function of this method of repair. Patients' ages ranged from 18 to 79 years (mean age 48.7 years). Mitral valve insufficiency was due to degenerative disease in 113 patients (58%), rheumatic disease in 74 (38%), ischemia and other causes in eight patients (4%). A total of 188 patients (9.7%) were in New York Heart Association class III or IV preoperatively and 94 (48%) had atrial fibrillation. The patients were divided into three functional groups: type I (normal leaflet motion), 35 patients (18%); type II (leaflet prolapse), 147 patients (75%); and type III (restricted leaflet motion), 13 patients (7%). The techniques included prosthetic ring annuloplasty (185 patients), leaflet resection (158 patients), chordal shortening (89 patients), leaflet mobilization (10 patients) and papillary muscle reimplantation (2 patients). Long-term follow-up was available in 189 patients (96.8%), for a rate of 2316 patients per year. The 15-year actuarial and valve-related survival rates were 72.4% and 82.8%, respectively. At 15 years, 93.9% of the patients were free from thromboembolism, 96.6% free from endocarditis, 95.6% free from anticoagulant-related hemorrhage, and 87.38% free from reoperation. Actuarial rate of freedom from reoperation was higher in the group with degenerative disease (92.7%) than in the group with rheumatic disease (76.12%). Among the 157 survivors, 117 (74%) were in New York Heart Association class I and class II and 105 (66%) were in sinus rhythm. Doppler echocardiographic studies showed normal ventricular contractility in 134 patients (84.5%), absence of mitral regurgitation in 112 (74%), trivial regurgitation in 27 (17%), and significant regurgitation in 4 patients (2.5%).