A 80 year old man, in general good health, presented with a rapidly progressive congestive heart failure, without response to treatment. At echocardiography, there were masses in the right atrium and ventricle. The patient deceased two months after the first clinical manifestations. At autopsy, we found a massive right-sided atrio-ventricular infiltration by a malignant non-Hodgkin's lymphoma of centroblastic type, causing a subtotal obstruction of the tricuspid and pulmonary valves. We observed also four intestinal metastases without other manifestations of lymphoma.