The content of the products of lipid peroxide oxidation in the plasma of blood flowing from the brain was higher in patients with moderate and severe craniocerebral injury than in patients with no marked functional and metabolic disorders. The concentration of these products in the cerebrospinal fluid was still higher. In patients with severe craniocerebral injury there was also an increase in the content of free fatty acids in blood flowing from the brain and in the content of ferrous iron ions in the cerebrospinal fluid. The intensification of the processes of lipid peroxide oxidation in the brain may play an essential role in determining the severity of the traumatic damage.