It is now well established that the systemic blood pressure is variable and that it reacts to various forms of external and internal stimulation. Such fluctuations of the blood pressure have contributed to the difficulty in determining normal blood pressure. Robinson and Brucer1have emphasized the difference of opinion as to what is normal blood pressure and have attempted in an extensive statistical study to determine more exactly the range of normal blood pressure. I have thought that if the range of variability of the blood pressure should be considered in addition to the level of blood pressure of any moment, some of the difficulties of determining whether or not an individual had normal blood pressure would be obviated. To use this conception, criteria for the normal range of blood pressure must be established. Some progress has been made regarding this through the use of standard tests for measuring