The number of patients carrying an endocavitary pacemaker is increasing every day. The presence of a foreign body in right cavities predisposes to the formation of thrombi that can be over infected from distal septic focci usually silent. When a pulmonary embolism is diagnosed in these patients, the initial study must include an echocardiographic exam in order to rule out the presence of an intracardiac thrombosis as the origin of the emboli. We present the case of a patient with and endocardiac pacemaker who was admitted with fever and repeated episodes of pulmonary embolism. Hemocultures were positive for proteus mirabilis and a electrocatheter thrombosis was demonstrated in bidimensional echocardiography. Proteus mirabilis was positive in cultures from the material obtained by cardiothomy and clinical evolution after surgery was satisfactory.