The authors report the case of a young 26 years old man admitted for abundant fluid pericarditis which was rapidly recurrent, requiring two perocardial punctures and a surgical drainage. The two dimensional echocardiogram demonstrated a large right atrio-ventricular tumour with infiltration of the right ventricular wall, suggesting its malignant nature. After confirmation by right angiography and in view of the rapid cardiovascular deterioration, it was decided to operate. The surgery was only exploratory; not even palliative surgery was possible for this tumour mass invading the right atrium, the right ventricle and the pericardium. Histology revealed it to be an angiosarcoma.