Artificial pacemakers are electronic devices used primarily to control cardiac rate in patients in whom the intrinsic heart rate is inadequate for a normal life style. These devices automatically and rhythmically provide electrical impulses to stimulate the heart. Electrical stimulation of various organs of the human body was already in practice more than two centuries ago. These applications, however, were in experimental stages until recently when electrical stimulation of the heart has emerged as a new therapy. In view of the astonishing progress made in the field of pacemaker technology and the current indications for the specific types of pacing systems, it behooves physicians caring for patients with heart disease to become familiar with the use of cardiac pacemakers and the not infrequent problems associated with their use. The primary purpose of this review is to present fundamental knowledge in the electrical stimulation of the heart and the various pacing systems available.