During the past year in this country and for some time previously abroad, there has been great interest in the restoration of normal mechanism by the action of quinidin sulphate in cases of auricular fibrillation. The present series of sixteen cases has been studied with special reference to the improvement in efficiency of the circulation following restoration of the normal rhythm, as judged by various subjective and objective criteria. Obviously, the fact that auricular fibrillation can be terminated is of little significance unless the health of the patient is thereby improved. In general, the following routine of treatment was employed: The circulation was brought to the highest efficiency possible by rest, and in most cases by thorough digitalization. Two patients who had slow cardiac rates with no pulse deficit, cyanosis or edema, and whose only signs of cardiac insufficiency were dyspnea and limitation of activity, were not given digitalis. In