Electromagnetic signals from various sources may cause interference with pacemakers. The safety systems developed by manufacturers are generally effective. Nevertheless, some electromagnetic sources, particularly those found in the medical environment, can induce transitory or permanent pacemaker dysfunction. This paper presents the various sources of electromagnetic signals to which a pacemaker may be exposed. Taking into account the available literature, it attempts to clarify those which are really deleterious for the pacemaker and how to avoid them.