The physical causes or mechanism of the systolic murmur and its clinical significance have been matters of much discussion for many years. There was a time, not so very long ago, when on hearing a systolic murmur over the heart, even in the absence of any other important abnormalities, the physician would pronounce the ominous verdict that the patient was suffering from organic heart disease with mitral insufficiency. He would also imply in this diagnosis a serious prognosis and institute restrictions in the mode of life for his patient. More recently, systolic murmurs have been found so often to be benign that an entirely opposite point of view has developed. It has become the teaching in many localities that "systolic murmurs have no significance whatever," that "organic mitral insufficiency does not exist except with mitral stenosis" and even that "auscultation is of no great importance," for it is not the