Clinical experience with permanent transvenous pacing during a 6 year period at Hannover Medical School is presented. A total of 1,376 pacemaker operations were performed in 799 patients, with a mortality rate of 1.1 per cent. The most common complications were premature battery failure, dislocation of endocardial electrodes, infections of the generator and/or electrodes, and skin ulcerations. In our cumulative follow-up period of 1,225 years, a complication necessitating a reoperation is to be expected after an average function-time of 31 months. Including normal battery exhaustion in this calculation will make reoperation necessary every 21.9 months.