The kidney acts as a long-term regulator of blood pressure and controls the extracellular sodium and water balance. Significant renal mechanisms of blood pressure regulation are the renin angiotensin system, renal sympathetic activity and sodium excretion. Animal work and clinical studies show that mental stress affects the renal plasma flow and urinary sodium excretion. In spontaneously hypertensive rats environmental stress resulted in sodium retention, triggered by increased renal sympathetic nerve activity, which is the development of arterial hypertension. In a pilot study in subjects at risk for developing arterial hypertension, the investigator observed a lower sodium excretion by mental stress. In healthy volunteers, a 30-minute mental stress test resulted in increased glomerular filtration rate, filtration fraction and an increase in urinary sodium excretion.