We describe two patients with primary cardiac malignant lymphoma involving the right atrium and superior vena cava, resulting in intractable right cardiac failure and superior vena cava syndrome. Patients were diagnosed by surgical myocardial biopsy and were treated with combination chemotherapy for non-Hodgkin's lymphoma. Each attained a marked response, and hence avoided sudden death from tricuspid atresia. Both have remained alive for more than 21 and 34 months, respectively, and continue intermittent combination chemotherapy.