A 69-year-old man while being treated for type B aortic dissection was also found to have acute myocardial infarction. The patient initially was treated conservatively. Prophylactic anticoagulant treatment of potential thrombosis was not given because of aortic dissection. Stent-graft implantation to the thoracic aorta was considered at the time. Unexpectedly, elective computer tomography (CT), revealed 2 large thrombi at the bifurcation of the pulmonary trunk. The patient did not show any symptoms of pulmonary embolism. Heparin therapy was initiated immediately. The patient responded well to the therapy and on transesophageal echocardiography and subsequent CT no embolic material was found. Since that time, the patient is receiving oral anticoagulation. The case we present raises the question of anticoagulation prophylaxis in the presence of aortic dissection in bedridden patients. Failure to use such therapy in our patient could have resulted in an unfavorable clinical outcome.