After fracture of his toes, a 34-year-old male patient developed deep leg vein thrombosis and subsequent pulmonary embolism. Because of progressive heart enlargement, 2D-echocardiography was performed. A floating mass measuring 4.5 cm X 3.5 cm was found in the right ventricle. On account of the deep leg vein thrombosis and the lung perfusion deficits detected by scintigraphy, the floating mass was thought to be a thrombus. Because of the severity of the patient's state and the lack of success of a heparin therapy with 32,000 IU/d, fibrinolytic treatment with streptokinase was started. After initial improvement in pulmonary gas exchange the patient died about 7 hours later from progressive cardiopulmonary insufficiency. Necropsy revealed a smaller right ventricular thrombus than that seen by echocardiography. There were typical surface erosions caused by the fibrinolytic treatment. Many younger and older emboli which in part were fragmented could be shown in the pulmonary vessels. A fragmentation of the right ventricular thrombus and subsequent lethal occlusion of pulmonary vessels had to be considered. With respect to the course of the described case and some case reports in the literature we think fibrinolysis is more dangerous than surgical thrombectomy in right ventricular thrombosis.