The intracranial pressure (PIC) of two children with Reye's sundrome aged 9 years 7 months and 4 years 7 months was monitored for 9 and 5 days respectively with a subdural device. This provided a useful guide to the treatment that was necessary to reduce the very high intracranial pressure. One of the patients died of uncontrollable raised intracranial pressure (HIC). This monitoring technique should be used in all cases of HIC.