Interleukin (IL)-4 levels in the internal jugular vein were measured during the acute stage in patients with head injuries, subarachnoid hemorrhage, or intracerebral hemorrhage to investigate the prognostic value. Levels of IL-4, interferon (IFN)-gamma, glucose, and lactate, and oxygen saturation were measured in the internal jugular vein to investigate cerebral local reactions and in the radial artery as a control at admission and 4 hours after onset. The subjects were divided into a survival group and a deceased group. IL-4 levels were high in the internal jugular veins and arterio-jugular venous differences in oxygen content (AjDO(2)) were low at 4 hours after onset in the deceased group. Increased glucose and lactate levels were found at 4 hours after onset in the deceased group. No significant difference was found for IFN-gamma. The severity of cerebral disorders evaluated using AjDO(2) showed a negative correlation with intracerebral IL-4 level. This finding suggests that secretion of IL-4, which has a neuroprotective effect, may increase with the severity of neuropathy and may be useful as a prognostic index.