A SEX dependent urinary protein in the rat has been described by Roy and Neuhaus^{1â 4}. This protein is an α2-globulin (α2U) of hepatic origin and has a molecular weight of 26,400 (refs. 2 and 3). It is rapidly excreted in the urine³. The level of α2U in blood is therefore very low (< 3 mg per 100 ml. blood)³. This protein is absent in females and immature male rats. The synthesis of α2U is very sensitive to hormonal manipulations⁴. Treatment with testosterone of the spayed females induces its synthesis whereas treatment of adult male rats with oestradiol brings about a complete repression⁴. A quantitative immunological method for the assay of α2U has been described³. All of these above mentioned properties make α2U a very convenient system for studying the possible hormonal control of gene action in the mammalian system. In this communication we report our studies on the requirement of the pituitary gland for the androgenic induction of α2U in spayed rats.