PIP: Growth in weight, length, and head circumference were compared among 3 different groups of infants. These measurements for each group were also compared to those presumed representative for the average fetus and infant of corresponding gestational age. A graph was prepared to show curves of fetal growth in the 3 parameters for the last trimester of pregnancy and through the 1st year of life after the equivalent age of "term" has been reached. The composite curves of the 3 groups were compared from the time of birth with no correction for gestational age. Since 1962 all low birthweight infants admitted to the Premature Center of the University of Oregon Medical School have been measured longitudinally for weight, length, and head circumference. 3 weight gestation groups were selected for study: Group A, very premature with weight appropriate for gestational age, gestation 27-29 weeks, birth weight .95-1.30 kg; Group B, moderately premature, with weight appropriate for gestational age, gestation 31-33 weeks, birth weight 1.40-2.00 kg; and Group C, full term, but severely underweight for gestational age, 38 weeks or more, birth weight less than 2.00 kg. Weight was obtained from an automatic Toledo balance scale, accurate to 10 gm. The babies were weighed prior to the morning feeding. Since measurements could not be made at precisely the same age for all infants after discharge from the hospital, derived measurements for appropriate intervals of time were extrapolated from the curves of growth of each infant. For estimation of fetal growth in weight, length, and head circumference, data were obtained from measurements reported in the literature for infants of known gestational age. After a 2-week lag, the curves for weightand length of Groups A and B paralleled those for standard fetuses and infants thoughout the 1st year of life. The curves were at a lower level with the curve of the most immature group (A) being reduced the most. Head circumference, after a 2-week lag, regained and followed the projectedcurve, suggesting a temporary acceleration in the growth of the head. This was in contrast to growth in length. Growth in Group C, after a lesser interruption following birth, also paralleled the mean curves of full-sized infants, but at a level substantially below them as well as those forthe Groups A and B. The curve for head growth in Group C gradually approached that of full-sized infants, but the significant disparity in head size from the normal-sized infant at birth was only partly reduced by the end of the 1st year. From the data it appears that little, if any, of the retardation in weight and length that may be suffered in the fetal or neonatal period is made up during the 1st year of life if the infant's age is corrected to term.