This report summarizes a meeting sponsored by the National Institute of Child Health and Development to review important scientific contributions over the past several years that addressed the causes and consequences of intrauterine growth restriction (IUGR). IUGR contributes significantly to perinatal morbidity and mortality. Considerable research has focused on various aspects of fetal growth, particularly with respect to the epidemiology of IUGR, the regulation of fetal growth by intrinsic growth factors and extrinsic nutrient supply, the role of the placenta in fetal growth, and diagnosis and treatment of IUGR. In addition to summarizing many of the advances in each of these important areas of research, a major purpose of the meeting was to consider future directions for research into the causes, consequences, diagnosis, and treatment of IUGR. At the onset of the meeting, Dr William Hay provided a broad overview of IUGR. Much of the impetus for studying IUGR began with the observation by pediatricians and neonatologists that when classified according to birth weight and gestational age, newborn infants were shown to be small, average, or large for gestational age (SGA, AGA, and LGA, respectively), and that specific morbidities and rates of death were unique to each of these birth weight-gestational age classifications.1 SGA infants, for example, were recognized as having more frequent problems with hypoglycemia, hypothermia, polycythemia, and neurodevelopmental handicaps, as well as a higher mortality rate.2 With the advent of improved fetal diagnosis, infants who were small at birth were increasingly recognized as representing a variety of fetal growth patterns. For example, infants who were considered constitutionally small simply grew parallel to, but less than, the 10th percentile for normal rates of fetal growth. Infants with genetic abnormalities or acquired diseases, particularly infections occurring in the first trimester, also grew slowly, and many of these infants …