The considerable evolution in technique and hardware, occurred over the past three decades, has greatly simplified the implantation procedure of pacemakers and cardioverter-defibrillators. Indeed, the introduction of relatively simple and safe methods of central venous access, and the miniaturization of the generator with subcutaneous placement have facilitated the implantation. However, inherent with cardiac pacing and defibrillating therapy is the potential for the occurrence of an early or delayed untoward event. Although skill, experience, and technique are all mitigating factors, every cardiologist should know potential complications and should be able to stratify overall risk related to a device implantation. Thus, both the implanting physician or the clinical cardiologist must be concerned not only with measures to avoid complications, but also with their early recognition and treatment.