1. The diurnal excretion of sodium and potassium was observed in young people, with and without a genetic predisposition to hypertension, both in the presence and absence of psychological stress. 2. In the absence of stress, the normal day/night sodium excretion ratio was reversed in the children of hypertensive parents. This was significantly less than day/night sodium excretion in children of normotensive parents. A similar finding was observed for day/night potassium excretion. 3. There was a significant negative correlation between systolic blood pressure and day/night sodium excretion in children of hypertensive parents but not in children of normotensive parents. 4. After the mental stress of a University examination day/night sodium reverted to normal in children of hypertensive parents.

1. Basal levels of pulse rate, blood pressure and rates of sodium and potassium excretion were observed in eight white male patients with mild hypertension and eight age-, sex- and colour-matched controls during an initial rest period of 90 min and then for 5 h after a 1 h period of isometric exercise involving all four limbs in rotation. The studies were repeated on another day with the subjects resting instead of exercising for 1 h. 2. Changes in systolic pressure after exercise were similar in the hypertensive and control groups, whereas the rise in diastolic pressure was higher and the rise in pulse rate lower after exercise in the hypertensive group compared with the control group. 3. The changes in the rate of salt excretion were significantly different in the two groups, the hypertensive group retaining proportionately more sodium and potassium over several hours.