Noninvasive measurement of intracranial pressure is now available via the anterior fontanel in newborn infants. We measured intracranial pressure during the first week of life in 18 preterm infants and found a statistically significant increase from birth to age 24 hours and a significant decrease by 48 hours (13.8 vs. 24.4 vs. 14.3 cm H20). This did not seem to be the result of postnatal head shrinkage. There were no other apparent correlations. We suspect that hypoxia may play an important role in the etiology of increased intracranial pressure. We believe that these findings may have important implications for intracranial hemorrhage in preterm infants.