Blood pressures have been measured, and sociological, anthropometric, medical, and biochemical examinations have been made in an isolated group of !Kung bushmen in northern Botswana. Blood pressures were taken in 152 bushmen of both sexes, aged 15 to 83 years, who were examined in family groups. Systolic and diastolic pressures declined with increasing age in the men. The women showed a small rise of systolic pressure after the menopause but their diastolic pressure decreased slightly with age. The mean blood pressure (diastolic + 1 3 pulse pressure) for men and women combined thus remained the same throughout life. Other communities whose blood pressures do not increase with age are reviewed. Of the possible explanations in the bushmen, a low salt intake and a lack of obesity appeared to be important, with relative freedom from mental stress an additional imponderable factor. © 1972.