Much has been written with regard to errors in human blood pressure measurements connected with such factors as rigid arterial walls, a too narrow cuff, etc., or the choice of the criteria for determining when pulse waves begin to pass under the cuff or when the diastolic pressure is reached; but heretofore little attention has been paid to the personal factor which operates in the identification of the various criteria. Since it is the large amount of individual judgment involved in "guessing" blood pressure by feeling of arteries, which has led to the general adoption of instrumental methods, it is important to inquire, in addition to other sources of error, how large this personal element may be when blood pressure instruments are used. Oscillatory criteria both for systolic and diastolic pressure, which have been advocated for use with several highly authorized instruments and which have been widely accepted