Non-Hodgkin's lymphoma is common in patients with human immune-deficiency virus infection, but an intracardiac localisation is rare. In this case, the malignant lymphoma presented with a degradation of the patient's condition and signs of right-sided cardiac failure. Echocardiography showed a polylobed mass invading the right ventricle. Computerised tomography provided detailled information of the extension of the lymphoma in the different cardiac chambers. The patient died after a few days of a low cardiac output state. The malignant nature of the tumour was confirmed at biopsy. This case of cardiac lymphoma in a patient with immunodepression confirms the fatal character of this condition in the very shea term after the appearance of the first clinical signs, the value of echocardiography in the diagnosis and the difficulty in implementing any effective therapeutic measure.