A uniform characterization applying to all patients with repetitive tachycardia, or status tachycardiacus, is hardly justifiable. This group of patients is heterogeneous in morphology, in prognostic implication and in management. It is in childhood and youth that the essence of this disorder seems to manifest itself, undiluted by admixture with various conditions incidental to the aging process. But repetitive tachycardia as observed in adults is not quite the same condition. Here it is not necessarily benign; it is commonly associated with organic heart disease, occasionally in its terminal phase. And it is difficult if not impossible to separate those effects that are due to repetitive paroxysmal tachycardia from those due to complicating disease. Repetitive tachycardia is frequently observed in neurotic patients, Repetitiveness may develop as a phase in patients with a long-standing history of classical tachycardia. Prophylaxis is very much on a trial-and-error basis; occasionally it seems successful but more often all measures are only partially or temporarily effective.