The behaviour of arterial blood pressure and heart rate after an active change from the supine to the upright posture was studied in the aged. A significant decrease in the average values for systolic and diastolic blood pressure and a significant increase in the average values for heart rate in the first minute of the upright posture were observed. The systolic and diastolic pressures are reduced in a higher percentage of the cases in the 80-94 year age class. In the same class the PAS is more frequently reduced in the male and the PAD in the female. The heart rate, in the upright posture, is higher in 80-94 year-old males without a significant difference between the sexes.