Alpha2u globulin is an androgeninducible and estrogen—repressible adult rat urinary protein of hepatic origin. Androgen treatment of immature rats of both sexes before 40 days of age does not induce α2u globulin. Administration of corticosterone along with testosterone also fails to induce α2u globulin in immature rats. Castration of newborn rats at 3 days of age does not prevent the development of androgen sensitivity after maturation. Urinary level of α2u output in adult male rats after partial hepatectomy closely follows the pattern of hepatic regeneration. From these results it is concluded that, (I) two independent events, gonadal maturation and development of androgen sensitivity in the liver cells seem to coincide around 40 days of age and, (II) once the liver cells acquire androgen—sensitivity through aging processes, the property can be transmitted from parent to daughter cells. (Endocrinology92: 957, 1973)