[Truncated abstract] Therapeutic Radiation has been used for the treatment of cancer and other diseases for nearly a century. Over the past 20 years, Hyperbaric Oxygen Treatment (HBOT) has been used to assist wound healing in the prevention and treatment of the more severe complications associated with the side effects of Therapeutic Radiation Treatment (TRT). The use of HBOT is based on the premise that increased oxygen tissue tension aids wound healing by increasing the hypoxic gradient and stimulating angiogenesis and fibroblast differentiation. As it takes up to 6 months for a hypoxic state to develop in treated tissue, following radiation treatment, current recommendations for HBOT state that it is not effective until after this time. During this 6 month period, immediately following TRT, many specialized tissues in or adjacent to the field of irradiation, such as salivary glands and bone, are damaged due to a progressive thickening of arteries and fibrosis, and these tissues are never replaced. Currently, HBOT is used to treat the complications of TRT, but it would be far better if they could be prevented . . . In summary, this experimental model has fulfilled its prime objective of demonstrating that HBOT is effective in reducing the long-term side effects of therapeutic radiation treatment in normal tissue, when given one week after the completion of the radiation treatment and statistically disproves the Null Hypothesis that there is no difference in the incidence of postoperative complications or morbidity of TRT when 20 intermittent daily HBOT are started one week after completion of TRT. This project provides an extensive description of the histological process and also proposes a hypothesis for the molecular events that may be taking place.