1. The initial heart rate (HR) response evoked by standing up and 70° head-up tilt from the supine resting position, as well as the changes in HR and blood pressure after 1–2 min in the upright position, was analysed in teenage boys (aged 10–15 years) and healthy old men (aged 60–90 years).
2. Standing up induced a characteristic temporary HR increase that lasted 20 s and far exceeded the gradual initial HR rise induced by head-up tilt. The main effect of age on the initial HR transients was a definite diminution of the response.
3. After 1–2 min standing and tilting, young subjects showed a pronounced increase in HR and diastolic pressure with little change in systolic pressure. In contrast, old subjects showed a lesser increase in HR and diastolic pressure and a decrease in systolic pressure. A fall in systolic pressure of greater than 20 mmHg after 1 min of active standing was, however, not observed.
4. It is concluded that the circulatory adjustment to the stress of postural change differs markedly between young and elderly subjects. In healthy old subjects marked postural hypotension appears to be rare.