A solvent extraction method is described that is simple and avoids use of evaporation at elevated temperatures. The extraction procedure gives 90‰ recovery of total steroids from whole blood. Extraction and chromatography give 50‰ recovery of individual steroids from whole blood. The method has been applied to the identification of steroids in rat adrenal vein blood. Some reactions of a steroid slightly more polar than corticosterone are described; the indication is that it has the basic configuration of ll-desoxy-17-hydroxycorticosterone, with some additional molecular modification. Evidence is given to support the presence of 11-dehydrocorticosterone, and the presence of corticosterone has been confirmed beyond reasonable doubt. The method has also been applied to the quantification of steroids in rabbit adrenal vein blood. Total A4-3-ketosteroidoutput averaged 22 µg.⁄ml. blood or 64 µg.⁄adrenal⁄kg.⁄hr. over a collection period of three to four hours. Steroid output per unit volume of blood was relatively constant throughout the collection period.