Evidence is presented that auscultatory gaps heard in patients with arteriosclerotic heart disease may be associated with a reduced blood flow to the extremity. Further reduction of such flow, as by application of a tourniquet. increased the likelihood of a gap. Contrariwise, increase in extremity blood flow eliminated the gap in every instance. Vibrations are present in the gap range, but these are subaudible; electronic amplification may bring these sounds to audible levels.