This issue of Cardiac Electrophysiology Clinics, edited by Drs. Luigi Padeletti and Giuseppe Bagliani, will cover the latest in Normal Electrophysiology, Substrates, and the Electrocardiographic Diagnosis of Cardiac Arrhythmias. Topics covered in this issue include History of Arrhythmias; P wave and arrhythmias originating in the atria; PQ interval and Junctional zone; QRS complex; Ventricular repolarization during arrhythmias; Classification and specific electrocardiographic pattern of Cardiac Arrhythmias; and Electrocardiographic practice of cardiac arrhythmias.