Considerable progress has been made on developing specific chromatographic procedures for prostaglandins and a specific radioimmunoassay of PGA1. Additionally, the metabolic clearance and calculated blood production rates suggest that the amount of this substance produced daily in man has biological potential activities in terms of blood pressure and sodium metabolism. Our aims, given adequate lab technician assistance, are to study the origin and fate of PGAl and PGA2 in normal and hypertensive man and to understand the possible inter-relationship between prostaglandins, blood pressure, sodium, and aldosterone production.