Implantation of a permanent pacemaker is the most commonly performed surgical operation involving the heart. Annually, 115,000 to 175,000 permanent pacemakers are implanted in the United States. The modern cardiac pacemaker is a complex device that can sense and pace in both the atrium and ventricle. Moreover, it modulates the pacing rate based on sensed physiologic parameters. This article reviews the fundamental principles of pacemaker technology and provides the emergency physician with approaches to common pacemaker problems.