Seventeen anephric patients who constituted the subjects of this study received renal allografts between the years 1969 to 1973. The renin-angiotensin-aldosterone mechanism was evaluated in relation to either a normotensive or hypertensive clinical state in these subjects. Group I (Controls) were normotensive and on a normal diet; Group II were normotensive, on sodium restriction for five days, followed by saline infusion on the seventh day; and Group III were hypertensive, on similar sodium restriction for five days, followed by saline infusion on the seventh day. Glomerular filtration rates and levels of plasma renin and aldosterone, and the secretion rate of the latter were obtained on appropriate days. These studies confirm that an intact renin-angiotensin-aldosterone relationship exists in human renal transplant patients. The presence of high aldosterone secretion rate without hypertension is a new but unexplained finding. The lack of correlation of high aldosterone secretion rates in our normotensive and hypertensive patients suggests that aldosterone does not play a detectable or significant role in the pathogenesis of chronic or sustained transplant hypertension.