Patterns of early postnatal growth were analyzed among low birthweight infants enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Infants were divided into four groups according to their neonatal status: (1) term, normal birthweight (NBW); (2) term, low birthweight (LBW); (3) moderately preterm LBW; and (4) very preterm LBW. Comparison of mean weight and length z-scores indicated that term NBW and very preterm LBW infants were at or near the national reference averages at 8, 12, and 18 months. Term LBW and moderately preterm infants were lighter and shorter than the other two study groups at each visit. Term LBW and moderately preterm infants displayed evidence of catch-up growth during the study period. Catch-up growth was defined as a decrease in the percentage of infants below the 10th percentile for weight. The effect of neonatal body proportions on postnatal growth was investigated in term LBW infants. The infants were divided into two groups based on their ponderal index (PI) at birth (low PI and proportionate PI). Comparison of weight and length z-scores indicated that both groups of term LBW infants improved in z-scores between birth and the first visit (approximately 8 months). However, infants with evidence of asymmetric intrauterine growth restriction (low PI) continued to improve in weight and length z-scores, whereas those with symmetric growth restriction (proportionate PI) remained lighter and shorter. Am.