The intracranial pressure was monitored via the anterior fontanel, using a noninvasive technique, in 78 acutely ill, 39 normal term, and 6 normal preterm infants. In normal term and preterm infants the anterior fontanel pressure (AFP) was 10.2 +/- 0.4 and 9.5 +/- 0.8 cm H2O, respectively. Infants with hyaline membrane disease had elevated pressure (13.3 +/- 0.6 cm H2O), which was higher than that of normal preterm infants. Following an episode of intracranial hemorrhage in four infants, the AFP increased to 26.2 +/- 2.5 cm H2O. Elevated pressure was noted in infants with meconium aspiration syndrome (24.1 +/- 1.8 cm H2O); the pressure decreased during the phase of recovery (15.6 +/- 3.5 cm H2O). Elevated pressure was noted in infants with meningitis and hydrocephalus. Repeated measurements helped to diagnose shunt obstruction in an infant with hydrocephalus.