In recent years numerous reports have appeared-for example, Pickering (1955)-of discrepancies between arterial bloodpressure measured by an intra-arterial method and by the usual cuff and sphygmomanometer. Part of this discrepancy has been attributed to the effect of arm circumference on arterial pressure measured with a cuff. Corrections based on measurements made by Ragan and Bordley (1941) have been published by Pickering, Roberts and Sowry (1954).While several workers report good agreement between systolic blood-pressure determined by the intra-arterial and that by the cuff method, there is disagreement over which of the two phases (phase 4, muffling, or phase 5, disappearance) represents the true diastolic pressure. Ragan and Bordley (1941) state that the pressure represented by sudden muffling (phase 4) of the Korotkoff sounds was usually higher than the intra-arterial pressure. Hamilton, Woodbury, and Harper (1936) found the diastolic pressure to be 9 mm. higher than the intra-arterial pressure when muffling was used as the end-point. Steele (1942) noted that the final cessation of sounds approximated to the intra-arterial diastolic pressure more closely than did muffling. However, Roberts, Smiley, and Manning (1953), using a strain-gauge manometer and an electromanometer (condenser microphone), concluded that muffling of the sounds bears a more constant and close relation to the " true " diastolic pressure. Van Bergen, Weatherhead, Treloar, Dobkin, and Buckley (1954) came to the same conclusion using a standard resistance wire pressure-transducer. The latter workers found that the disappearance of sound grossly underestimated the intra-arterial diastolic blood-pressure.Recent work (Holland, 1963 ;Rose, Holland, and Crowley 1964) has shown that blood-pressure measured by a normal sphygmomanometer can be affected by observer bias. The present comparisons of intra-arterial with cuff pressure were made using a London School of Hygiene sphygmomanometer (Holland, 1963) to avoid the possibility of observer bias. MethodIntra-arterial brachial-artery pressure was measured in the right arm by use of a Hansen (1949) capacitance manometer. This method has been utilized by Sharpey-Schafer (1955) Before starting the investigation the blood-pressure of subjects was measured simultaneously in both arms by two observers by connecting two cuffs to a common manometer via a T-junction. In no case was the difference between left and right arms greater than 5 mm. Hg.Intra-arterial blood-pressure was measured continuously during the course of the experiment. Cuff blood-pressure was

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A random sample of the population of Bergen, Norway, was examined in 1963/64 for blood pressure, weight and height in association with a chest X‐ray survey. The sample was made up of all individuals born on the 3rd, 13th and 23rd day of each month from 1864 to 1949, representing approximately 10% of the population 14 years of age and above, resident in Bergen on July 1, 1963. The study group comprised 8452 subjects, 3718 males and 4734 females. Of these, 8294 (98.1%) were actually examined, 7499 in survey centres and 795 in their private homes. The blood pressure measurements were carried out with a standardized technique by 19 specially trained and supervised nurses. The results have been analysed in detail with regard to observer variation. For each subject, two sphygmomanometers were used in alternating sequence; the cuff was 40 mm long and 14 cm wide. The results of the study are presented in seven figures and two tables; details are to be found in ten appendices. The systolic blood pressure was found to vary with sex and age, but very little with height, weight and pulse rate. In females, the mean values varied from 118 mm Hg in the age group 20–29 years to 171 mm at 70–79 years. In males, the mean values varied from 128 mm Hg at ages 20–29 years to 157 mm in the 40–49 year group. In the two diastolic pressures (phase 4 and phase 5) the same type of sex differences were present, but to a smaller degree. In females the mean values for the fifth phase increased from 66 to 82 mm Hg, and in males, from 69 to 82 mm. The systolic and diastolic blood pressures were well correlated in all age groups of both sexes. The subjects examined in their private homes showed slightly higher blood pressure values than those attending the survey centres. The reason for this difference was investigated, but no definite explanation was found.