Traumatic brain injury is an injury which can temporarily or permanently damage the brain function. Brain trauma has a relatively poor prognosis and such patients will often have reduced work ability and a high possibility to stay temporarily or permanently disabled. That is why such injuries are a major public health issue since even less severe brain injuries can result in permanent neuropsychological disorders that affect work ability and quality of life. Traumatic injury can be divided into two phases, primary and secondary. Primary injury is the result of the mechanical force that acts upon the head and brain structures. The development of secondary injury begins after the emergence of the primary and lasts for several days. During this period the damage increases and it is of vital importance to try to reduce the extent of the damage to the affected tissue. Hyperoxia is defined as a greater than normal oxygen percent in the tissues and organs, caused by increased delivery of oxygen or increased percentage o fit in the arterial blood. It can be achieved in normobaric and hyperbaric conditions. Normobaric hyperoxia is achieved under atmospheric conditions, whereas hyperbaric is achieved at pressures higher than atmospheric. In the treatment of traumatic brain injury, the main goal is to preserve brain function and reduce the extent of tissue damage. Most important thing is, except ICP control, to maintain proper tissue perfusion and to provide aerobic metabolism. Studies have shown that hyperoxia leads to improved oxygenation and increased aerobic metabolism of injured tissue. In conclusion, further research in this area is needed in order to clearly identify groups of patients that should be recommended for hyperoxia treatment.