The clinical, echocardiographic, hemodynamic, angiographic and pathologic features of five patients who had right heart thrombus are presented and their management is discussed. Two modes of presentation were recognized. In four patients, right heart thrombus complicated peripheral venous thrombosis and was associated with major pulmonary thromboembolism and right heart obstruction. In the fifth, it complicated myocarditis with heart failure and appeared to cause right heart obstruction. Two-dimensional echocardiography was diagnostic of right heart thrombus in four patients and showed evidence of right heart dysfunction in those with major pulmonary thromboembolism. The diagnosis was confirmed at surgery in three patients and at autopsy in one. Three patients successfully underwent surgical removal of the thrombus followed by anticoagulation. One patient was treated successfully with anticoagulation alone. The only death occurred in the patient with myocarditis.