Adenosine was identified in 1929 and immediately recognised as having a potential role in therapy for arrhythmia because of its negative chronotropic and dromotropic effects. Adenosine entered mainstream use in the 1980s as a highly effective agent for the termination of supraventricular tachycardia (SVT) involving the atrioventricular node, as well as for its ability to unmask the underlying rhythm in other SVTs. Adenosine has subsequently been found to have applications in interventional electrophysiology. While considered a safe agent because of its short half-life, adenosine may provoke arrhythmias in the form of AF, bradyarrhythmia and ventricular tachyarrhythmia. Adenosine is also associated with bronchospasm, although this may reflect irritant-induced dyspnoea rather than true obstruction. Adenosine is linked to numerous pathologies relevant to arrhythmia predisposition, including heart failure, obesity, ischaemia and the ageing process itself. This article examines 90 years of experience with adenosine in the light of new European Society of Cardiology guidelines for the management of SVT.