Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common regular supraventricular tachycardia in clinical practice. Pathophysiologically, this cardiac arrhythmia is based on a dual conduction property in the AV node. The paroxysmal symptoms typically include an on/off phenomenon, regular palpitations, and pulse-synchronous pounding in the neck area. The reentrant tachycardia can be interrupted by Valsalva maneuvers or adenosine administration. Electrocardiographically, it presents as a narrow complex tachycardia with an unrecognizable or retrograde P wave. In the electrophysiology (EP) lab, typical AVNRT must be differentiated from atypical forms of AVNRT as well as from concealed WPW syndrome or focal atrial tachycardias. In symptomatic AVNRT, ablation/modulation of the slow pathway is the therapy of choice with a low complication rate and excellent prospects of success. This chapter describes the characteristics of AVNRT as well as techniques for differential diagnosis and ablation treatment in the EP lab.