There has always been an appreciation of the role of Purkinje fibers in the fast conduction of the normal cardiac impulse. Here, we briefly update our knowledge of this important set of cardiac cells. We discuss the anatomy of a Purkinje fiber strand, the importance of longitudinal conduction within a strand, circus movement within a strand, conduction, and excitability properties of Purkinjes. At the cell level, we discuss the important components of the ion channel makeup in the nonremodeled Purkinjes of healthy hearts. Finally, we discuss the role of the Purkinjes in forming the heritable arrhythmogenic substrates such as long QT, heritable conduction slowing, CPVT, sQT, and Brugada syndromes.