Tricuspid valve insufficiency may contribute to a poor hemodynamic result after mitral valve replacement. To determine the role of surgical treatment, we have reviewed the records of 32 adult patients who underwent tricuspid valve repair or replacement 4 months to 14 years after mitral valve replacement. Mild tricuspid valve insufficiency at the time of mitral valve replacement was present in 21 patients (66%); 26 patients (81%) had New York Heart Association class IV disability. Tricuspid annuloplasty was performed in 16 patients, and the remainder received various prosthetic valves. Concomitant repair of mitral valve periprosthetic leak and/or replacement of the aortic valve was necessary in 18 patients (53%). Hospital mortality was 25%, and all early deaths were related to low cardiac output. Among hospital survivors there have been 14 late deaths for 3 and 5 year actuarial survival rates of 65% and 44%. Twelve of the 14 patients who died late and one of 10 patients who were alive at the end of the follow-up period had little or no functional improvement after tricuspid valve repair or replacement. The high early and late mortality and poor functional outcome for patients undergoing tricuspid valve surgery late after mitral valve replacement contrast with our good overall results in reoperation for prosthetic heart valves. It appears that serious tricuspid valve insufficiency after mitral valve replacement frequently signals right ventricular failure and dilatation; restoring valve competence is palliative. This experience encourages us to continue our policy of liberal indications for tricuspid valve annuloplasty at initial mitral valve replacement.