The chapters in this book grew out of addresses given by distinguished doctors, scientists, and professors at a Seminar sponsored by the American Academy of Arts and Sciences in May, 1963. They present some of the latest research and discoveries in different fields bearing on population and fertility control. The problem is concisely summarized in the report on the growth of world population just published -by the National Academy of Sciences: "If the present world population should continue to increase at its present rate of 2% per year then within two centuries there will be more than 150 billion people. Fifty times the present number. . . ." The far-reaching significance of the problem and the critical importance of both fundamental and clinical research in this field are portrayed here. Information from every major division of the natural and social sciences must be examined before man can develop intelligent policies on population control. Chapters in this book, therefore, are contributed by experts in economics. sociology, and anthropology, as well as in physiology, gynecology, and other clinical and research branches of medicine.