The study of growth and development of adipose tissue can give important clues to understanding the pathogenesis of obesity, one of the major publi c health and nutrition problems of our so-called developed societies. In 1981 the American Committee on Nutrition drew attention to" the need for studies of the pathogenesis Of obesity in early life with an emphasis on the ontogeny of the fat organ.''~ Since then, little progress has been made in this area. There are still many difficulties in the study of adipose tissue in the human fetus. Thus the knowledge of fat tissue biology in humans is mostly indirect and leads to the problem of the relevance of animal data to man. We focus on the cellular processes and the metabolic influences that occur during the prenatal and postnatal periods under normal and abnormal conditions. Especially important are the effects on adipose tissue growth of metabolic and dysmorph0genic disturbances such as maternal type I diabetes, intrauterine growth retardation, connective tissue dysplasia, and tumors. Our purpose is to