To define the role of functional tricuspid insufficiency and right ventricular (RV) failure in patients with mitral disease, the data of 121 patients with secondary tricuspid insufficiency that underwent mitral valve replacement (MVR) from January 1982 to December 1987 were analyzed. The mitral hemodynamic lesion was: stenosis in 41 patients (33.9%); insufficiency in 11 (9.1%) and mixed stenosis and insufficiency in 69 (57.0%). NYHA functional class was: II in 4 patients (3.3%), III in 78 (64.5%) and IV in 39 (32.2%). In 100 cases (group 1) with tricuspid insufficiency defined as moderate or severe, a De Vega annuloplasty was performed while in 21 (group 2) with mild tricuspid insufficiency, no tricuspid surgical procedure was performed. Hospital deaths occurred in 17 of 121 patients [14% (CL 10.8-17.0)]. There was no significant difference in hospital mortality between group 1 and group 2 (15% vs 9.5%; P = 0.75). Incremental risk factors for hospital mortality as determined by multivariate analysis, include: cardiothoracic ratio (P = 0.0016), total aortic cross-clamp time (P = 0.006), associated cardiac disease (P = 0.0209) and emergency operations (P = 0.0318). Mean follow-up of surviving patients was 50.1 +/- 28.1 months. Late deaths occurred in 16 patients [15.4% (CL 11.7-18.7)]. The actuarial survival rate was 85.6% and 73.8% at 5 and 9 years, respectively. Nine patients [8.6% (CL 5.9-11.3)] required reoperation. There was no significant difference between group 1 and group 2 in the rate of late cardiac related deaths (5.9% vs 5.3%, P = 0.66) and of tricuspid reoperations (4.7% vs 5.3%, P = 0.62).(ABSTRACT TRUNCATED AT 250 WORDS)