The determination of blood pressure is the third most important routine physiologic measurement that the modern physician uses with a fine degree of precision. While it does not carry an immediate purport in cases of acute illness as do the temperature and the pulse, yet for long range evaluation of the health of the average person it is far more significant. No other commonly used test gives such quick and reasonably exact information concerning life expectancy. With added information derived from the life history of the blood pressure and from mortality data a physician should be able to forecast the longevity or the general pathologic tendencies of many of his patients. There has been a tendency lately to belittle the taking of blood pressure, but with the generally accepted realization that at least one fifth of the population is hypertensive and bears the stigma of an ominous prognosis, the blood