Background and Purpose-Free radical hyperproduction may play an important role in brain hemorrhage and ischemia/reperfusion injury. The aims of this study were to assess whether antioxidant depletion occurs after intracranial hemorrhage (ICH) and head trauma (HT) and to evaluate the relation between the diameter of the brain lesion, the degree of the neurological impairment, and any observed antioxidant changes. Methods-We measured plasma levels of vitamin C (ascorbic acid, AA), uric acid (UA), vitamin E (␣-tocopherol), and ubiquinol-10 in 13 patients with ICH and 15 patients with HT on the day of the brain injury and subsequently every other day up to 1 week. Patients were compared with 40 healthy control subjects. Results-ICH and HT patients had significantly lower plasma levels of AA compared with healthy subjects, in contrast to plasma levels of UA, ␣-tocopherol, and ubiquinol-10. AA levels were significantly inversely correlated with the severity of the neurological impairment as assessed by the Glasgow Coma Scale and the National Institutes of Health Stroke Scale. AA levels were also significantly inversely correlated with the major diameter of the lesion. In addition, mean plasma AA levels were lower in jugular compared with peripheral blood samples obtained from 5 patients. Conclusions-These findings suggest that a condition of oxidative stress occurs in patients with head trauma and hemorrhagic stroke of recent onset. The consequences of early vitamin C depletion on brain injury as well as the effects of vitamin C supplementation in ICH and HT patients remain to be addressed in further studies. Key Words: antioxidants Ⅲ brain hemorrhage Ⅲ head trauma Ⅲ oxidative stress Ⅲ vitamin C I ncreased production of free radicals and reactive oxygen species (ROS) leading to oxidative stress 1 appears to play an important role in the pathogenesis of ischemic, 2,3 hemorrhagic, 4,5 and traumatic brain injury. 6,7 Studies in animal models of focal cerebral ischemia and reperfusion have demonstrated the presence of increased levels of ROS. 8 -11 ROS also probably contribute to brain injury in head trauma (HT) and intracranial hemorrhage (ICH) in humans, because hemorrhage is associated with the release of hemoglobinbound heme iron, which can participate in free radical reactions to produce ROS. 4,5,12 One possible consequence of excess ROS formation is lipid peroxidation. The brain appears to be particularly vulnerable to oxidative lipid damage because of its high content of polyunsaturated fatty acids. 13 Lipid peroxidation may alter the fluidity and permeability of neuronal membranes and thus, cellular functioning, or damage membranebound receptors and enzymes. 13 In brain hemorrhage, the presence of "free" iron 14 may favor the conversion of lipid hydroperoxides to lipid alkoxyl radicals, which can "reinitiate" lipid peroxidation and hence further expand the radical chain reaction. 13 In addition, tissue lactic acidosis can dramatically enhance ROS formation and lipid peroxidation in brain tissue, which in turn ca...