The papers contained in this volume were presented at the third meeting of the International Organization for the Study of Human Development, held in Madrid on September 21-24, 1975. The primary objective of the Organization is to bring together persons from a wide range of disciplines concerned with problems of human development. The first meeting typified this interdisciplinary approach by concentrating on problems relating to genetic expression. The second meeting considered milk and lactation from a variety of viewpoints, including those of the molecular biologist and the geographer. The present meeting deals with nutrition as an integral part of human life as well as a fundamental discipline in the area of biology. The editors wish to thank Professors Ettore Rossi and Fabio Sereni and Dr. Frank Falkner for their invaluable assistance in planning this conference, and would particularly like to express their appreciation toward Professor Cipriano Canosa and his staff for their gracious and hospitable assist ance in providing facilities and accommodations for the participants. The editorial assistance of Mary Lynn Hendrix has aided us in our contribution; and the secretarial support of Millie Fazzi and Natalie Stover is gratefully acknowledged.