Seventeen patients with lymphomatous involvement of the heart or pericardium were studied. The series includes eight patients with Hodgkin's disease and nine with non-Hodgkin's lymphoma. All 17 had radiologia evidence of pulmonary, or mediastinal involvement. Cardiac or pericardial disease in seven was apparently due to direct extension of other intrathoracic tumor masses. Cardiac involvement was usually a late manifestation of lymphoma with median onset 20 months after initial diagnosis. Fourteen patients had been treated for stage IV disease prior to the onset of cardiac lymphoma. Only seven of the 17 patients with cardiac involvement were diagnosed antemortem. Four of them are alive without evidence of disease 8 to 68 months after diagnosis and treatment. Because cardiac lymphomas may respond to therapy with prolonged survival, it is imperative that clinicians suspect cardiac or pericardial involvement in lymphoma patients who have radiographic evidence of intrathoracic lesions (especially adjacent to cardiac borders), unexplained tachyarrhythmia or conduction disturbance, evidence of outflow obstruction, or signs and symptoms suggesting pericardial effusion or tamponade.