The chest roentgenogram in a 46-year-old woman with dyspnoea for several months revealed global cardiac enlargement. Echocardiography demonstrated a tumour in the right atrium, about 4 x 5 cm, as well as circular pericardial effusion. Septic temperatures occurred in the further course, and blood cultures grew Staphylococcus aureus. Recurrent pulmonary emboli and cerebral emboli with hemiparesis, especially of the brachiofacial region, occurred despite heparinization. Shortly after hospitalization a chest roentgenogram revealed a round shadow, about 1 cm in diameter, in the left upper lobe. The patient died in cardiogenic shock on the 16th hospital day. Autopsy showed the tumour to be a poorly differentiated round-cell sarcoma, originating from the wall of the right atrium, infiltrating the myocardium through to the epicardium and extending to the tricuspid orifice. The foramen ovale was open, making paradoxical emboli at atrial level possible.