Studies have shown an inverse relationship between birthweight and blood pressure in later life. The objective of this study is to analyze the relationship between birthweight and blood pressure in childhood in a North American–based population. Data on 2,958 births with follow-up at 7 years of age from the Providence, RI, cohort of the Collaborative Perinatal Project of the National Institute of Neurological Diseases and Stroke were retrospectively analyzed using univariate and multivariate analytic methods. Bivariate analysis of the total cohort showed a direct relationship between follow-up weight at age 7 years and birthweight (r = 0.24; P < 0.001) and follow-up weight with systolic (SBP) and diastolic blood pressure (DBP; r = 0.33; P < 0.001 and r = 0.22; P < 0.001, respectively). On multivariate analysis, follow-up weight and height were the strongest predictors of SBP and DBP. There was also a significant inverse relationship between birthweight and SBP. A cohort of term infants (n = 2,561) was subdivided into birthweight-for-gestational-age groupings to further evaluate the effects of birthweight on blood pressure. Small-for-gestational-age (SGA) infants were markedly smaller at age 7 years than those large-for-gestational-age (LGA; 21 ± 4 kg v 26 ± 4 kg; P < 0.01). Despite the direct association between follow-up weight and blood pressure, the mean blood pressure did not differ between SGA (103/58 mm Hg) and LGA patients (103/59 mm Hg). To assess whether birthweight was an independent predictor of blood pressure, blood pressures were predicted using linear regression equations. For every 1-kg decrease in birthweight in term infants, SBP at 7 years increased by 1.3 mm Hg and DBP by 0.6 mm Hg. In conclusion, controlling for weight and height in term infants at 7 years of age has an inverse linear effect on blood pressure. This suggests that birthweight in relation to gestation may be a contributor to the multifactorial cause of essential hypertension.