The surgical treatment of primary malignant lymphoma of the heart in a 43-year-old man is reported. The tumor was extensively resected together with the right atrial wall and both venae cavae, and the resulting defect was repaired with a bovine pericardial patch. The postoperative course was fairly stable for more than 7 months following surgery, under a regular chemotherapy regimen. The patient died of acute pneumonia on the 234th postoperative day. The autopsy findings confirmed the diagnosis of primary malignant lymphoma of the heart.