Adult female hypogonadal mice, in whom hypogonadism is secondary to a genetic deficiency in hypothalamic gonadotropin-releasing hormone (GnRH), are infertile. Mating, pregnancy, and delivery of healthy litters were achieved after transplantation of normal fetal preoptic area tissue, a major site of GnRH-containing cell bodies, into the third ventricle of adult female hypogonadal mice. Immunocytochemistry revealed GnRH-containing neurons in the grafts and GnRH-containing processes extending to the lateral median eminence of the host brains.