In an attempt to clarify the indications for tricuspid valve operations, we studied 150 patients who had preoperative and postoperative full catheterization including biventriculography. Seventy-eight patients had organic and 72 had functional tricuspid insufficiency (TI). One hundred nineteen underwent tricuspid repair (46 commissurotomies and 115 annulopasties), and in 31 the tricuspid disease was surgically ignored. Ninety seven percent of all patients with hemodynamically correct left-side repair were in Class I or II, regardless of the state of the tricuspid valve. Repair of lesions on the left side determined the postoperative cardiac index. In the "repaired group," 38% had residual gradients and 30% residual TI. Eighty percent of patients with low postoperative pulmonary resistance had no TI, compared with 53% with high pulmonary resistance. In the "ignored group," all 14 patients with organic disease had residual TI, as did nine of 17 with functional disease but with elevated pulmonary resistance. The right ventricular end-diastolic volume (RVEDV) decreased 37% in the "repaired" (p < 0.001) and 36% in the "ignored" group (p < 0.01) if tricuspid competence was achieved, but remained high if TI persisted. Because of these data, which emphasize the need for an early and correct repair of the left-side lesions, we believe that (1) functional TI can be ignored only in patients with predictable and significant reduction in pulmonary resistance and (2) organic disease must be repaired.