Fontanelle pressure (FP) and cerebral perfusion pressure (CPP) were measured continuously for the first 5 postnatal days in 21 preterm neonates. A new application device for use with the sensor of an intracranial pressure monitor allows accurate, continuous FP measurement. Accuracy of the technique was established by comparing results using the new device with 14-h continuous intraventricular pressure recordings from four infants before ventricular shunting. Agreement between the two techniques was satisfactory with the mean difference being 0.4 mm Hg. FP rose on each of the first 5 days after birth. CPP also rose over the 5 days but there were periods during suctioning of the endotracheal tube, crying, and vigorous activity when CPP was very low.