Statistical researches of blood pressure measurement have been conducted by many persons. In those researches, however, the extraction of examines may be considered rather partial as the representatives of normal Japanese.<br>In order to reveal how the blood pressure varies in accordance with age and what relations there exist between various conditions and the blood pressure, by measuring the blood pressure systemastically with the normal healthy Japanese as the objective person, the author has therefore pursued the present study as follows:<br>First of all, when the author examined, as a preparatory experiment, if the blood pressure would vary in accordance with the time of measurement, from the average measured value of the examinees, the author found out that the result was not significant statistically, and that the variation of individual measured value were comparatively negligible in the morning.<br>So the measurement time was set in the morning.<br>Next, the author investigated whether or not the blood pressure would vary in accordance with the position of the examinee (lying, sitting on a chair or standing), and the author perceived a statistically significant differenc in the maximum blood pressure was measured, the examinee being set down on a chair.<br>It was also examined whether or not the measurement would differ according as the examiner was rich in experience or not, from which it was revealed that even a medical student with little experience could obtain as precise a result as a physician of 30 years' experience.<br>The author asked for the collaboration of a physician rich in bedside and clinical experiences as well as that of a medical student. The medical sudent was trained in blood pressure measurement especially for the present purpose.<br>After the method of measurement was investigated by the prepartry experiments above, the examinee extraction was schemed as follows. In case of the examinees be extracted according to the theory of arbitary specimen extraction, the number of examinees to be measured can be got from the next formula.<br>n=4S²/b²<br>Here, n indicates the required number of examinees, S the standard deviation of the blood pressure, b the absolute accuracy which indicates the error of average value of measurement, that is, how many mmHg of fluctuation of the blood pressure is allowed. This formula is applicable in case which the population is almost limitless in its scope and the accuracy of results is 95%.<br>The author set the absolute accuracy within 1mmHg for up to 50 years of age and within 2mmHg for above 50 years of age and got the required number of examinees in each grade of age, replacing in the formula the standard deviation of the highest blood pressure of man by 5 year-grades from the data of Watanbe etc, thus the author measured the blood pressure of each of 4, 280 examinees of both sexes, that is 8, 560 persons in all. These examinees were reclassified, furthermore, according to the rate of the occupational working population and local population; the measurement of the blood pressure was carried out in 12 places: Tokyo City, Kumamoto City, Kamaishi City, Akita City, Maebashi City, Moji City, Minami-Akita-gun (Akita Pref.), Ogasa-gun (Shizuoka Pref.), Kita-Gumma-gun (Gumma Pref.), Kita-Kambara-gun (Niigata Pref.), the environment of Sakaide City (Kagawa Pref.) and Usa-machi (Kôchi Pref.).<br>The measurement was carried out in the following order: first, the examiner asked the examinees about their age, frequency of pregnancy, dieting, luxuries. condition of work, weight and height, physical conditions, anamnesis, etc in detail. Then came the measurement.