Studies were made on the effects of prenatal administration of androgen on the development of sexual function in female rats. Pregnant rats at the middle or late stage of gestation were injected subcutaneously with testosterone propionate(TP) or methyltestosterone(MT) and their embryos at the late stage of intra-uterine life were given a single direct injection of TP In pregnant rats, an injection of 3 or 6mg MT or TP, given for 6 successive days beginning on the 12th or the 15th day of gestation did not affect ovarian function of the offspring, although it was effective in causing masculinization of the genital tract. The female young became pregnant by artificial insemination.