One day after implantation of a permanent pacemaker in an 82-year-old man, transthoracic echocardiography showed a mass in the right ventricle and a small pericardial effusion. Transesophageal echocardiography revealed a mass attached to the pacemaker lead. Subcutaneous administration of enoxaparin was begun, and the patient remained free of symptoms for the duration of his hospital stay Follow-up echocardiography performed before discharge failed to show the right ventricular mass, but a lung perfusion scan revealed multiple bilateral perfusion defects consistent with pulmonary emboli. The patient was discharged on a regimen of enoxaparin for another 30 days. Two years later, he remained asymptomatic.