We measured the effect of posture on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in eight patients admitted with grade 4 hepatic coma due to fulminant hepatic failure complicated by renal failure. Upward head elevation greater than 20 degrees did not consistently reduce ICP; instead, ICP increased in three patients who later died of cerebral edema. CPP was reduced significantly by elevation greater than 20 degrees, falling to less than 50 mm Hg in those patients who subsequently died of cerebral edema. Our study does not support the current practice of nursing patients with hepatic coma, who are at risk of dying from cerebral edema, in head-upright postures greater than 20 degrees.