Traditional classifications of atrial tachyarrhythmias include not only rhythm disturbances arising primarily within the atria, but also a variety of dysrhythmias in which it is now recognized that participation of both atrial and nonatrial tissue is required. For example, atrial flutter and atrial fibrillation are believed to arise principally as the result of electrophysiologic disturbances within the atria. On the other hand, in paroxysmal atrial tachycardia caused by reentry within the AV node, the precise contribution of the atria to the reentry loop is unclear, whereas in paroxysmal atrial tachycardia caused by reentry utilizing an accessory AV connection, both ventricles and atria are equally critical to maintenance of the reentry circuit. In order to avoid the confusion associated with the conventional classifications of atrial tachycardias, we prefer to consider those arrhythmias in which the atria are the principal site of electrophysiological disturbance as 'primary' atrial tachyarrhythmias. These 'primary' atrial arrhythmias are the subject of this article. Other supraventricular tachycardias, in which nonatrial or AV nodal tissue is critical to sustaining tachycardia, are classified separately by specific diagnosis and are not discussed here.