This report presents the results of a study of the blood pressure of 5757 apparently "healthy" white men and women 65 years of age and older in the United States. Frequency distribution curves of the blood pressure show that the factor of lability of pressure was not a source of error in the group. After the age of 65, the blood pressure does not show a consistent rise with advancing years, as it does below this age. The mean systolic pressure in both sexes continues to rise slightly until the 70-74 years, when the highest level of the mean systolic pressure is reached (159 mm Hg among women). After the age of 74 the systolic pressure in women declines slowly for 10 years; it falls more definitely after the age of 85, reaching the lowest level in the 95-year group (149 mm Hg). The average systolic pressure in men remains essentially constant-145 mm Hg after the 70-74 years. The sex difference is greatest in the 70-74 year group, when the systolic pressure in women is 14 mm Hg higher than it is in men. The lowest sex difference (5 mm Hg) is found after the age of 95. Thus, the systolic pressures of both sexes approach each other in extreme old age, but always remain slightly higher in the female. The diastolic blood pressure is practically constant after the age of 65 in both sexes, with minor exceptions; it is highest in the 65-69 year group, and is very slightly higher in women; in men, the mean is 83 mm Hg, in women 85. After the age of 69, the diastolic pressure declines slightly but continuously, falling to 78 mm Hg in men, and to 81 in women after 95th year. This difference of 2 to 3 mm Hg is not of practical significance. Two ranges of blood pressure have been computed for each sex between the 65th and 106th years. The middle 80% range in males is [image] and in females is [image] In general, if blood pressures fall within these limits and are not associated with evidence of hypertensive heart disease, antihy-pertensive drug therapy is not indicated. The middle 95% range in males is [image], and in females is [image]. A blood pressure reading beyond these figures is practically always abnormal.