Sixteen cases of auricular flutter have been observed in the Mayo Clinic by us during the last thirty months. In the study of these cases a review of the literature revealed certain features which made it seem desirable to record our findings. The paucity of case reports in the literature is ample evidence that the condition is frequently overlooked. Definition. —Auricular flutter may be described as an acceleration of the auricles to a rate beyond 200 per minute.1 In all reported cases such acceleration has been accompanied by a partial heart block, giving a ventricular rate of one-half, one-third or one-fourth of the auricular rate, or a total dissociation of rhythm (complete heart block); or the degree of block may vary between the auricular beats, giving a gross ventricular arrhythmia. The partial block is apparently due to the inability of the auriculoventricular bundle to conduct impulses so rapidly, or to