Various opinions exist regarding the incidence, the time of onset and the relation of auricular fibrillation to the course of hypertensive heart disease. Janeway1stated that of 212 deceased patients with hypertensive cardiovascular disease (nephritis included) only eight had auricular fibrillation, and of 246 living patients only two had this arrhythmia. White2reported that, in a group of 708 cases of hypertensive heart disease, auricular fibrillation was present in ninety-two (13 per cent), in fourteen of which it was paroxysmal in type. Under a discussion of the cardiac manifestations of essentialhypertension, Lewis3stated that established auricular fibrillation occurs in a number of cases but is observed particularly late in the disease. Fahr4differed with this opinion and stated that in some cases the onset of auricular fibrillation brings forth clinical evidence of heart failure. He added that it is the most common form of arrhythmia