Hyperbaric oxygen therapy (HBOT) is defined as the use of oxygen at higher than atmospheric pressure for the treatment of underlying disease processes and the diseases they produce. Modern HBOT in which 100% O2 is breathed in a pressurized chamber dates back to the 1930s, when it was first used for treatment of decompression illness in divers. There are currently 13 FDA-approved uses for HBOT, including decompression illness, gas gangrene, air embolism, osteomyelitis, radiation necrosis, and the most recent addition—diabetic ulcers. HBOT can dramatically and permanently improve symptoms of chronic TBI months or even many years after the original head injury. This assertion is generally met with skepticism within the medical establishment because we have been taught for generations that any post-concussion symptoms persisting more than 6 months or so after a head injury are due to permanent brain damage that cannot be repaired.