In this, our second edition of Reproduction in Mammals, we are responding to numerous requests for a more up-to-date and rather more detailed treatment of the subject. The first edition was accorded an excellent reception, but Books 1 to 5 were written some 14 years ago and inevitably there have been many advances on many fronts since then. As before, the manner of presentation is intended to make the subject matter interesting to read and readily comprehensible to undergraduates in the biological sciences, and yet with sufficient depth to provide a valued source of information to graduates engaged in both teaching and research. Our authors have been selected from among the best known in their respective fields. Book 5 is concerned with the many ways in which we can now manipulate reproductive processes in animals and humans, thanks to our new understanding of hormone action and improved control over early developmental events. We have at our disposal a whole array of synthetic hormone agonists, antagonists and antibodies that can be used at will to stimulate or inhibit fertility in animals and humans alike, so that productivity in livestock can be promoted according to plan and child-bearing becomes more a matter of choice than chance. We can compensate for infertility by in vitro fertilization and embryo transfer, and overcome inherent deficiencies by techniques involving embryo manipulation. Existing barriers to the dissemination and application of this new-found knowledge are discussed in some detail, since it is becoming increasingly clear that improvements in the quality of life for people in many developing countries will be long delayed unless they can meet essential needs and call a halt to runaway population growth.