Out of a series of 1,734 pacemaker patients, the clinical course of 46 patients was reviewed in whom a functionless endocardial electrode was retained. Non-infected electrodes (25 patients) were generally well tolerated without complications, except in one patient who experienced fatal catheter embolism into the pulmonary artery. In cases of infected electrodes (21 patients) a mortality rate of 25% was encountered due to septic complications. Catheter migration was fatal in two out of three patients. It is concluded that entrapped electrode catheters should be removed by thoracotomy if persisting infection is present or if catheter migration has occurred.