PIP: A short review of research in hypothalmic releasing factors emphasizes their isolation, characteristics, and molecular structure and their application to fertility control. The hypothalamus regulation of the pituitary's gonadotropic secretion has been identified as taking place in a special type of capillary vessel which unites the area of median eminence of the hypothalamus to the anterior lobe of the pituitary. This hypophysiotropic area secretes the hypothalamic hormones (LH, FSH, etc.) that are small polypeptides with two important characteristics: 1) extremely powerful effect in miniscule doses, and 2) extreme specificity of action. The latter is particularly important in contrast to steroids (estrogen, progesterone, etc.) presently used, whose generalized effects cause side reactions in oral administration. Use of these highly specific hypothalamic hormones could be completely free of side effects. The LH-releasing factor has been synthesized, and research indicates use of this hormone as a means of restoring fertility through its effect on LH and FSH production. Fertility control is indicated by either using the LH-releasing factor to precisely date the time of ovulation, providing accuracy to the rhythm method, or through development of a synthetic LRF antagonist to prevent fertility by inhibiting the LH-releasing factor. This could be done orally with a pill taken only once per month. Further research is continuing.