The present study aimes at producing the objective proof of blood pressure.

To record Korotkov sound crystal micro-phone and electromagnetic oscillograph were used and amplifier was non filter type, Cuff pressure was recorded by 1 mmHg scale simltaneously.

This standard pattern of K-sound with decreasing cuff pressure consists of Tone-segment and Noise-segment. The existence of Tone-segment had a wide range from systolic blood pressure to diastolic, and Noise-segment exists within the limits of Tone-segment. And the range of the existence of K-sound and its wave form is due to individual variation, further more it is unsettled with the same person.

As a results of considerration of the fact as described, 1) the existence of positive or negative spike which appears in the first wave of Tone-segment, especially steep up rising spike is regarded as the pressure index of systolic blood pressure, 2) the last wave with　notch which appears in Up-slope of the wave of Tone-segment is regarded as the pressure index of diastolic blood pressure.