Due to its negative chronotropic and inotropic effects, adenosine has to date been considered as a cardiodepressant agent. However, adenosine increases ventricular automaticity. This review by Jesus Hernández and Alexandre Ribeiro discusses the experimental and clinical evidence for the excitatory effects of adenosine on ventricular automaticity, as well as the possible mechanisms involved in the ventricular dysrhythmias that occur during the diagnostic and therapeutic use of adenosine.