The appearance of a 1:1 mechanism, i. e., the ventricle beating at the same rate as the auricle, is uncommon in patients with auricular flutter. Usually there is some degree of block at the junctional tissues which determines the rate of the ventricular response. However, under some circumstances not at present clearly understood, conduction through the auriculoventricular bundle is raised, and every auricular contraction spreads to the ventricle, causing it to beat at a rate seldom seen in any other condition in man. For example, in the case here recorded the rate during attacks was 272 a minute, as determined from electrocardiographic records. Similar elevations in ventricular rate have been recorded in children by Lewis<sup>1</sup>and by Koplik,<sup>2</sup>and in adults by Mackenzie,<sup>3</sup>by White and Stevens,<sup>4</sup>and by Blackford and Willius.<sup>5</sup> <h3>REPORT OF CASE</h3> V. R., a man, aged 25, a mechanical engineer, first