We report a case of atrial fibrillation induction after the use of adenosine for the termination of supraventricular tachycardia in the emergency department. Atrial fibrillation is not an uncommon side effect of adenosine administration. Hemodynamic collapse may occur if an antegrade-conducting accessory pathway allows for a rapid ventricular response. Therefore, we would recommend that the use of adenosine be limited to situations in which there is appropriate electrocardiographic monitoring and emergency resuscitative capabilities.