This monograph represents the eighth sponsored by the International Society for Biochemical Endocrinology. The topics should be of interest to basic research scientists, medical practitioners, and students of repro ductive biology. It complements our monograph published in 1979 on Structure and Function of the Gonadotropins. The monograph is organized in ten topic areas relative to the general theme of reproduction and contraception. There are several chapters in each area. Obviously, all aspects of each area could not be covered. An attempt was made to seek interesting basic research ideas and concepts that might in the future be applicable to fertility regulation. The topics are: interactions in gonadotropin regulation; GnRH analogues as contra ceptive agents; receptors in cellular localization of hormones; uterine and mammary receptors; germ-cell regulation and secretory proteins; control mechanisms and metabolic regulations; hCG peptides and anti sera as antifertility agents; ieutinization, oocyte maturation, and early pregnancy; steroids and cell growth; and finally, prostaglandins and cell function. The studies encompass many disciplines and techniques in anatomy, physiology, biochemistry, and endocrinology in animals and humans, both in vitro and in vivo. A conference of contributors was held in Maine at the Asticou Inn in Northeast Harbor during the week of September 9-13, 1979. The chapters as written for the monograph were presented for discussion by the participants, who were selected for their knowledge of, and contri butions to, this area of scientific investigation.