The carcinoid syndrome is a common sequela in patients with carcinoid tumor metastatic to the liver. Cardiac involvement occurs in 19-56% of patients with symptomatic carcinoid syndrome and, in some patients, leads to valvular surgery to relieve symptoms due to progressive right-sided heart failure. Reports of these patients have emphasized amelioration of cardiac symptoms, but postoperative tumor status rarely has been discussed. This report describes four patients who underwent valvular heart surgery for severe carcinoid heart disease and had regression of their metastatic carcinoid tumor postoperatively. All four patients had definite clinical improvement in cardiac function and relief of symptoms related to congestive heart failure postoperatively. Unexpectedly, they also had regression of their metastatic disease, as reflected in decreased levels of urinary 5-hydroxyindoleacetic acid, and objective evidence of a reduction in the size of hepatic metastases. To the authors' knowledge, these four patients represent the first reported cases of metastatic disease regression after valvular surgery for carcinoid heart disease. Further descriptions of tumor status in patients having undergone a heart operation for this disease would be valuable in determining the clinical significance of this finding.