The relationship between low birth weight, intrauterine growth retardation, and preterm delivery in infants born at a perinatal center is described. Between 20% and 30% of infants born weighing 500 to 2000 gm and nearly 50% of infants born weighing 2001 to 2750 gm had intrauterine growth retardation. For infants within the same low-birth weight group, infants with intrauterine growth retardation had one half to one sixth of the neonatal mortality rate of non-growth-retarded infants. However, only in the 501 to 1000 gm group did the difference in mortality between infants with and without intrauterine growth retardation substantially influence the composition of the group of survivors. © 1985.