The atrioventricular junction consists of the atrioventricular node and the bundle of His up to its division. All tachycardias arising in these structures or which depend on these structures for their sustenance are called "junctional". There are four main types. The first three correspond to reciprocating rhythms, nodal tachycardia, tachycardias using an accessory pathway with unidirectional retrograde conduction, and chronic reciprocating atrioventricular nodal tachycardia. All varieties of reciprocating atrioventricular nodal tachycardia have been well studied and their diagnosis is possible from the standard surface electrocardiogram from the position and morphology of the P' wave. They are accessible to radical treatment by radiofrequency ablation of the slow pathway or accessory pathway, when present. The definitive treatment of ectopic atrioventricular nodal tachycardia is not yet established and has to be considered case by case, this form of arrhythmia being rare.