The field of cardiac pacing has developed exponentially in the past several years. The widespread use of atrioventricular synchronous pacemakers has resulted in the recognition of several types of pacemaker-associated arrhythmias. Certain of these arrhythmias follow asynchronous stimulation of either cardiac chamber; others are the result of the artificial bypass tract created with dual-chamber sensing and pacing. All the arrhythmias, however, are associated with normal pacemaker function.