The clinical importance and the finding of only a rare reference in the English language to the auscultatory gap in sphygmomanometry indicate the need of a detailed presentation of the subject. For this purpose we have studied thirty cases. The auscultatory gap, "le trou auscultatoire" of the French, is that interval of absolute or relative silence occasionally found on listening over an artery during deflation of the blood pressure cuff; it usually begins at a variable point below the systolic pressure and continues for from 10 to 50 mm. of mercury. LITERATURE In 1917, Cook and Taussig1 reported a period of complete silence during the second phase of determination of blood pressure by the auscultatory method. They estimated that this phenomenon occurred in 5 per cent of hypertensive cases. In 1918, Tixier1a noted a short zone of silence below the systolic pressure. In 1919, Gallavardin and Tixier2 recorded one case