The annual meeting of the Perinatal Biochemical Group of the Spanish Biochemical Society held in Madrid on December 15-16, 1989, provided an excellent opportunity to bring together a group of distinguished investigators both from Spain and from abroad with a common interest in developmental endocrinology and biochemistry. The aim of the symposium was to present and discuss the most recent developments in the areas of endocrine and biochemical processes critical to normal growth and maturation of the newborn. To achieve a high degree of interaction among the participants, subject reviews as well as short communications were include in the program. The reviews provided in-depth information on selected important topics. The purpose of short communications was two fold: (i) to provide a forum to discuss on-going investigations on related areas; and (ii) to present opportunities for active participation by young investigators. This format proved very successful in generating fruitful discussions among the participants. Taken together the review chapters and the short communications have resulted in a coherent and unified subject presentation. Advances in biochemistry, molecular biology and cell biology have provided not only new and exciting experimental approaches but also have opened up new directions in the investigation of differentiation and developmental processes at cellular, molecular and biochemical levels during the early stages of growth and maturation. In recent years a wealth of information in these areas of development has emerged at a rapid rate.