The association of birthweight with length at 12 mo and with height at different ages was assessed in a sample of 260 healthy adolescents (130 boys and 130 girls). The longitudinal study included measures on body weight and height at 4, 6, 12, and 14 yr of age. Birthweight is highly correlated with stature at 14 years, particularly in male adolescents. Longitudinal principal components analysis (LPCA) showed that it is also correlated with the growing process. There is also strong evidence that birthweight can be a good predictor of the onset of the pubertal maturation process.