This essay is designed to review some of the basic and more recent contributions to our understanding of supraventricular tachyarrhythmias, their mechanisms, pertinent points in diagnosis, and treatment. Supraventricular tachycardia is discussed under the concept of reentrant mechanisms versus accelerated ectopic pacemakers. Atrial fibrillation and flutter, multifocal atrial tachycardia, supraventricular tachyarrhythmias associated with brady-tachy syndrome, and supra-ventricular tachycardias in ventricular preexcitation are likewise discussed. An outline of the different forms of therapy for refractory supraventricular tachyarrhythmias is provided.