Supraventricular tachycardias (SVTs) affect all age groups and are a source of significant morbidity. They are frequently encountered in otherwise healthy individuals without structural heart disease. Advances in the understanding of their mechanisms and anatomical locations have led to highly effective pharmacologic and nonpharmacologic treatment strategies. Recognition, identification, and differentiation of the various SVTs are of great importance in formulating an effective treatment strategy. Developments over the past four decades have made possible the accurate diagnosis of SVTs, and technological advances have led to ablative cures of most of these arrhythmias. This monograph provides an in-depth discussion of the history, presentation, mechanism, and treatment strategies of the most commonly encountered SVTs. The monograph is divided in two parts. Arrhythmias and related syndromes that are covered in detail in the first part include atrioventricular nodal reentrant tachycardia, Wolf-Parkinson-White syndrome, and atrioventricular reentrant tachycardia. The remaining SVTs are covered in the second part, which is presented here.