The relationship of the rate of intrauterine growth of low-birth-weight infants (1,501 to 2,500 gm) to their postnatal growth up to 10 years of age was investigated. Each child was assigned to one of four gestation quartiles which have identical birth weight distributions but differ widely in their length of gestation. The mean heights and weights of the children in each of the four quartiles were compared with similar data of a control group of children who had birth weights above 2,500 gm. Only infants in the long gestation quartile failed to catch up in height and weight to the control group by the end of the 10-year period. The same results that were obtained for the total cohort were also found separately for white and black children and for boys and girls. The data relate to 488 single white and black low-birth-weight infants and 488 normal-birth-weight infants.