1. Frequent measurements of arterial pressure, cardiac output, heart rate and body weight were carried out in three hypertensive anephric subjects during the reversal of hypertension by carefully controlled stepwise fluid withdrawal over a period of 24 days.
2. The initial 5% decrease of body weight was associated with decrements of arterial pressure and total peripheral resistance of 15 and 35% respectively, whereas cardiac output had risen by 25%. After a further decrease in body weight by 5%, arterial pressure was lowered another 15% without a change in total peripheral resistance, and cardiac output had returned to base line.
3. These data do not support the concept that whole-body autoregulation is an important factor in the pathogenesis of renoprival hypertension.