Thirty-six of 68 consecutive patients with fulminant hepatic failure (FHF) progressing to grade 4 encephalopathy who had extradural ICP monitors inserted were reviewed to determine the safety and the value of ICP monitoring. Only minor complications were encountered. These included local wound bleeding at the burrhole site in four patients and a small cerebral hemorrhage in relation to the monitor in one other patient. No significant long-term sequelae were related to the operative procedure. ICP monitoring identified rises in ICP unaccompanied by clinical signs and as a consequence treatment was given to the monitored patients more often than the non-monitored group (median 6 vs. 2 treatments, P < 0.01). The duration of survival from the onset of grade 4 encephalopathy was significantly greater in the ICP monitored group (median 60 vs. 10 h, P < 0.01) although overall survival was unchanged. Monitoring also provided important prognostic information since the peak ICP was higher in non-survivors than in survivors (median 45 vs. 35 mmHg, P = 0.051). The pattern of clinical signs accompanying episodes of intracranial hypertension differed between survivors and non-survivors. Pupillary abnormalities were detected more often in non-survivors while systolic hypertension occurred more frequently amongst survivors with the peak systolic blood pressure being significantly higher. ICP monitoring proved safe and effective, provided valuable information regarding subclinical intracranial hypertension and prognosis and should be regarded as part of the routine management of intracranial hypertension complicating FHF.