Stages of increased cerebral blood flow accompany stages of rapid brain growth The existence of stages of rapid brain growth implies the existence of associated stages of increased cerebral blood flow (CBF) to supply the substances and energy needed for the added brain weight. Studies in the literature give developmental data for CBF in humans which show stages of increased cerebral blood flow at ages starting just preceding and/or coincident with the ages of the rapid brain growth stages. Confirmation of the implication for one of the earliest stages is also found in PET data. Additionally, data for rodents show a similar association of stages of increasing CBF and their brain growth stages. Thus, to the accuracy of the data, the implication is confirmed. Finding stages in cerebral blood flow predicts the existence of stages of brain growth. In addition; finding correlated blood flow stages also supports the age spans of the stages of rapid brain growth in both species. Such correlations also suggest that measurements of blood flow anywhere in the body might serve to reveal rapid growth stages in particular localities or organs if the blood flow shows significant stages. The ratio of energy consumed in brain to that in total body decreases from close to 100% at birth to the adult value of about 20% by age 18 years.