Right heart failure in patients with carcinoid heart disease is a serious prognostic sign. Consideration and adequate timing of valvular operations seem essential for the postoperative outcome. Without any relation to duration or progression of the metastasizing tumor disease, right heart failure developed and increased rapidly for a period of 12 to 17 months in four patients with classic carcinoid syndrome. Invasive hemodynamic and cardiac ultrasound investigations revealed severe carcinoid heart disease, and medical decompensation treatment gradually failed. Tricuspid and pulmonic valve replacement operations resulted in dramatic improvement in three of the patients, and these patients were still free of cardiac symptoms 10, 12, and 38 months postoperatively. One patient died 5 days postoperatively probably of septicemia. The preoperative and postoperative development of the cardiac disease is evaluated clinically, by cardiac ultrasound and plasma atrial natriuretic peptide concentrations, and related to the tumor disease. Surgical anatomy and operative technique are reported, and the beneficial value of prophylactic treatment of the effects of tumor-released vasoactive substances by a somatostatin analog is emphasized.