This issue of Medical Clinics of North America, guest edited by Dr. Otto Costantini, is devoted to Cardiac Arrhythmias. Articles in this important issue include: Basic principles of cardiac electrophysiology; The electrocardiogram: Still a useful tool in the primary care office; Palpitation: Extended electrocardiogram monitoring: Which tests to use and when; Inherited cardiac arrhythmias/channelopathies; Antiarrhythmic drugs: Benefits and risks; Stroke prevention in atrial fibrillation: Anticoagulants and/or devices; Pharmacologic and non-pharmacologic management of atrial fibrillation; Supraventricular tachycardia; Ventricular tachycardia with and without structural heart disease; Cardiac Devices: Pacemakers, Defibrillators and Biventricular Devices; Brady-arrhythmias; When is syncope arrhythmic?; Sudden Cardiac Death: Who is at risk?; and Arrhythmias and Congenital Heart Disease. A CME program is also available for this title.