The implantation of a pacemaker is an everyday medical procedure. New indications are under evaluation. However, it should be recalled that this is a surgical intervention with implantation of a prosthesis with possible complications. This should, therefore, be a considered decision. There are early complications which occur in the first 6 weeks after implantation. Their incidence is underestimated (up to 7%) as is their seriousness. There are late complications. Some are responsible for pacemaker dysfunction, the risk of which is proportional to the dependence of the patient on permanent cardiac pacing. The migration of a pacing catheter or the fracture of an Accufix catheter expose the patient to much greater risk. Venous complications are overlooked as they are usually asymptomatic. The superior vena cava syndrome is, however, a serious complication of cardiac pacing. Two recent studies (MOST and DAVID) underline the deleterious haemodynamic effects of unnecessary right ventricular pacing. This right ventricular pacing may have a pro-arrhythmic effect on the ventricles and be responsible for sudden death. It may also cause atrial arrhythmia even if atrio-ventricular synchronisation is preserved. Infectious complications are also under-reported, partially because of the difficulty of diagnosis. They may be life-threatening and require extraction of the implanted material. In conclusion, it is wrong to think that even if a patient does not benefit from his implanted device this cannot have deleterious consequences. Pacemakers should be adjusted especially to avoid inappropriate right ventricular stimulation.