This is a study of 159 patients with tricuspid incompetence (TI) associated with a mitral or mitro-aortic valve defect. The mean age of the patients at operation was 25.5 years. The TI was left untreated in 84, corrected by semi-circular annuloplasty in 39, and corrected by a prothesis in 28, by a Carpentier ring in 6, and by Kay's plasty in 2. The 33 early deaths (21%) are regrettable. The long-term outlook was studied with a mean follow-up period of 26 months. The overall mortality rises, if these are included, to 42 (26%). By comparing the preoperative findings in those with good and poor results, we have been able to identify a certain number of risk factors: a preoperative course of greater than or equal to 6 years, a number of attacks of cardiac failure greater than or equal to 3, a cardiothoracic ratio greater than or equal to 0.70, a mean right atrial pressure greater than 12, a mean pulmonary arterial pressure of greater than or equal to 50. Severe TI is also a poor prognostic factor. If the three groups of patients are compared, bearing in mind the fact that their preoperative state was very similar, and that the TI was either left untreated or repaired by annuloplasty or prosthesis, it appears that such a correction improves neither the surgical mortality nor the long-term prognosis. It therefore seems to us that a functional TI can be treated expectantly since its resolution depends more on the unified treatment of the whole underlying disorder and on the state of the myocardium than on any localised correction of the TI.