Objectives To study the determinants of functional tricuspid regurgitation (TR) progression after surgical correction of mitral regurgitation, including the influence of mitral valve (MV) repair (MVr) versus replacement (MVR) for degenerative mitral regurgitation. Methods From January 1995 to January 2006, 747 adults with MV prolapse underwent isolated MVr (n = 683) or MVR (n = 64; mechanical in 32). The mean age was 60.8 years, and 491 were men (66.0%). Moderate preoperative functional TR was present in 115 (15.4%). The MVR group had a greater likelihood of New York Heart Association class III or IV (75.0% vs 34.4%, P < .001), atrial fibrillation (20.3% vs 8.3%, P = .002), a lower left ventricular ejection fraction (61.0% vs 65.2%, P < .003), and a higher pulmonary artery pressure (50.1 vs 41.2 mm Hg, P = .001). The patients were monitored for a mean of 6.9 years (MVr) or 7.7 years (MVR; P = .075). Results During late follow-up, no difference was found between the groups in the development of moderately severe or severe TR: 1 to 5 years (3.0% vs 3.3%, P = .91) and >5 years (6.1% vs 6.5%; P = .93). The univariate predictors of severe TR after 5 years were older age (hazard ratio [HR], 1.1; P = .011), female gender (HR, 6.86; P = .005), higher pulmonary artery pressure (HR, 1.05; P = .022), and larger left atrial size (HR, 2.11; P = .035). Two patients (0.26%) who had undergone initial MVr required reoperation for late functional TR. Another 2 patients had had the tricuspid valve addressed concurrent with reoperation for MVr failure. No tricuspid reoperations were required in the MVR group. Conclusions The risk of TR progression was low after MVr or MVR for MV prolapse. Timely MV surgery before the development of left atrial dilatation or pulmonary hypertension could further decrease the risk of TR progression during follow-up.