In reporting a case of haemangiosarcoma of the right atrium the authors emphasize the problems encountered in the diagnosis of primary tumours of the heart. The patient was a 50-year old woman who complained of digestive disorders and palpitations. Physical examination showed signs of right heart failure associated with a systolic murmur on the right side of the sternum. ECG gave normal results. Echocardiography displayed a pouch with liquid ultrastructure communicating with the right atrium. Angiography confirmed the presence of a cavity with irregular borders communicating with the right atrium. Coronary arteriography showed an abnormal disorderly distribution of the right coronary artery branches with newly formed vessels extending toward the tumour. At exploratory thoracotomy a large liquid tumour was found which bled at the slightest touch and was attached to the mediastinum and the right pericardium. The pleura and the lung contained several nodules of the same venous colour as the mother tumour. Extemporaneous biopsy and pathological analysis were in favour of a haemangiosarcoma. The patient died a few days after the thoracotomy.