The identification and treatment of dysrhythmias continues to be an evolving issue for the emergency medicine physician. Advances in electrophysiology and cardiopharmacology have enlightened the medical community to the ever-increasing complexity of cardiac arrhythmias, and pharmacologic interventions once reserved for cardiologists are now being incorporated into emergency department (ED) practice. This article reviews basic physiology, discusses classification schemes, and addresses pharmacologic interventions that have proved or potential benefit for common dysrhythmias.