It is commonly agreed that birth weight is associated with blood pressure in adults. However, not much is known about birth length, ponderal index, and early postnatal growth, whose effects on adult blood pressure, if any, can affect the interpretation of the birth weight-blood pressure association. This study examined the association between fetal growth, early postnatal growth, and blood pressure in Chinese adults. One hundred twenty-two subjects born in Hong Kong in 1967 were followed from birth to age 30 years. Multiple linear regression was used to analyze the association between size at birth, postnatal changes in body size, and systolic and diastolic blood pressure at age 30 years. Having adjusted for potential confounders and each other explanatory variable, it is found that birth length standard deviation score (regression coefficient or beta=-3.2), ponderal index at birth (beta=-1.8), and postnatal changes in ponderal index from age 6 months to 18 months (beta=-2.2) were inversely associated with systolic blood pressure (each P<0.05). Postnatal changes in length standard deviation score were not significantly associated with systolic blood pressure. Birth length standard deviation score was inversely associated with diastolic blood pressure at age 30 years (beta=-2.6; P<0.05). Other anthropometric variables were not associated with diastolic blood pressure. The results support the hypotheses that both fetal growth and early postnatal growth may have a long-term impact on blood pressure in adults. It also highlights the importance of differentiating length and weight for length.