At the same time the presence or absence of androgens is playing a critical role in genitalia development, the neuroendocrine mechanism of the central nervous system is also being influenced. Androgens present in sufficient amounts during the appropriate critical stage of development may program the central nervous system (CNS) to induce the potential for male sexual behavior. Experimental and analytical evidence suggests that a behavioral effect can be traced to this early androgen influence. Inappropriate fetal hormonal programming may contribute, therefore, to the spectrum of psychosexual behavior seen in humans. In addition, gender role is heavily influenced by assignment of sex of rearing follittleed by social interaction based upon genital appearance and the development of secondary sexual characteristics.