Adenosine, used to terminate paroxysmal supraventricular tachycardia (SVT), is often useful in understanding the mechanism of tachycardia. This case report describes induction of SVT with adenosine in a 36-year-old man presenting with recurrent palpitations. After a short run of conduction via both slow and fast pathways, SVT was induced following a long PR interval. The long PR interval resulted by conduction via the slow pathway due to the preferential conduction block by adenosine over fast pathway. The notching at the terminal part of QRS during antegrade slow pathway conduction and during tachycardia indicated activation of the atrium via retrograde fast pathway. This electrocardiographical feature confirmed the mechanism of the tachycardia as atrioventricular nodal reentrant tachycardia.