Of the 1050 pacemaker-implantations in the German Heart Centre in Munich from April 1974 to December 1977 complications arose in 229 cases necessitating a renewed surgical intervention. In accordance with the literature the dislocation of electrodes was the most frequent complication in the first days and weeks after implantation in our patients wil 11,1%. In cases of electrode dislocation the repositioning of the electrode is necessary; in certain cases an epi-myocardial electrode must be substituted for the usual transvenous electrode. Essential causes of complications were disturbances in woundhealing, necrosis of the skin and infection of the pacemaker-system, which were seen in 3,7% of all cases. In the case of infection of therapy of choice is the explntation of the pacemaker and the implantation of a new system in another position. Technical complications due to material are electrode fractures and battery defects. Complications due to material defects necessitate the exchange of the pacemaker or the electrode. Rare indications for reoperation were increase in threshold, muscle stimulation and allergi reactions caused by pacemakers.