The blood pressure of 327 men and women aged 46 to 54 years was related to birthweight, placental weight, length, ponderal index and head circumference at birth. All the subjects were born after 38 completed weeks of gestation. There were strong trends of higher blood pressure in adult life with lower birthweight (P = 0.04) and greater placental weight (P = 0.002). In subjects with placental weights of 1.25 lb or less, mean blood pressure, and the risk of hypertension, rose as ponderal index at birth fell (P = 0.0001). Mean systolic pressure rose by 13 mm Hg as ponderal index fell from greater than 14.75 to 12 or less. In those with placental weights above 1.25 lb, mean blood pressure, and the risk of hypertension, rose as length decreased and as the ratio of head circumference to length increased (P = 0.02). Mean systolic pressure rose by 14mm Hg as the head circumference to length ratio increased from less than 0.65 to greater than or equal to 0.7. These findings characterise the birth measurements of two groups of babies who are at increased risk of hypertension in adult life.