A selective number of electrocardiographic events occurring in cases of aberrant atrioventricular conduction (Wolff-Parkinson-White syndrome) are illustrated, and their significance briefly commented upon. The probability of an accessory conduction pathway between the auricles and ventricles is emphasized, and attention is drawn to some of the properties of this specialized conduction tissue. It is also pointed out that “vagotonia” is an essential attribute of the WPW syndrome, and is an important component in the electrocardiographic, as well as clinical, manifestations of cases with aberrant atrioventricular conduction.