In a longitudinal study of an unselected population of men and women standardized arterial blood pressure was measured at 70 and again at 80. At 70 the prevalence of arterial hypertension (greater than or equal to 160/95 mmHg) was 46% in men and 45% in women. At 80 it was only 19% and 30%. This decrease was partly owed to an increased ten year mortality in hypertensive 70 year old women. However, also a significant individual decrease was seen in the participants examined twice, - a decrease that did not seem connected to the increased use of antihypertensive medicine and was not connected to the presence of arteriosclerotic symptoms, but showed a connection to pathological ECG-changes at 80.