Transvenous endomyocardial biopsy is now well-established as the gold standard for evaluation of possible rejection episodes after cardiac transplantation. From 1985 to August 1992, 1990 patients have undergone 193 cardiac transplantations at Barnes Hospital. One hundred eighty-three patients survived their initial hospitalization and serve as the study group. Their records were reviewed for the purposes of identifying those with tricuspid regurgitation as a complication of right ventricular endomyocardial biopsy. These patients have undergone a total of 2,960 biopsies for an average of 16.2 biopsies per patient. Over a mean follow-up period of 4.22 years, all patients have been evaluated with standard two-dimensional echocardiograms. Mild to moderate tricuspid regurgitation was very common, but was thought to be biopsy-induced only if severe and accompanied by flail components of the tricuspid valve. Twelve patients were identified with this entity at our institution. Of these, 5 had no symptoms and were receiving no diuretics, 3 had mild symptoms consisting of lower extremity edema and continued to receive diuretics, 2 had moderate symptoms, and 2 had right heart failure and anasarca refractory to medical therapy. Both of the severely affected patients subsequently required tricuspid valve replacement. We conclude that the tricuspid valve apparatus is at significant risk of injury during endomyocardial biopsy, that most patients will be minimally symptomatic due to tricuspid regurgitation when this injury occurs, and that when the injury is accompanied by severe symptoms, the likelihood of improvement with medical therapy is small.