Data on the birth weight-blood pressure relationship are inconsistent. Although an inverse association has been suggested in several large studies, interpretation is complicated by publication and other biases. Few data are available on the relationship between other early growth measures and blood pressure. We examined the shape and size of association between determinants of fetal growth, size at birth, growth in infancy, and adult systolic and diastolic blood pressure at 31 years in the prospective northern Finnish 1966 birth cohort of 5960 participants. Birth weight, birth length, gestational age, ponderal index, and birth weight relative to gestational age showed a significant inverse association with blood pressure at age 31. Rapid growth in infancy ("change-up") was positively associated with blood pressure. Adjusted regression coefficients for birth weight indicated systolic/diastolic blood pressure lower by -1.7 (95% confidence interval [CI], -2.5, -1.0)/-0.7 (95% CI, -1.4, -0.02) mm Hg for 1 kg higher birth weight. The significant inverse association between birth weight and systolic blood pressure persisted without adjustment for adult body mass index for males. Among females, gestational age showed a stronger association with blood pressure than birth weight: gestational age higher by 7 weeks (equivalent to an average of 1 kg higher birth weight) among singletons associated with -2.9 (95% CI, -4.7, -1.1) mm Hg lower systolic blood pressure. Our results support the concept that birth weight, other birth measures, and infant growth are important determinants of blood pressure and hence cardiovascular disease risk in later life.