Hyperbaric oxygen is presently being used in an attempt to improve functional outcome following a multitude of brain injuries such as stroke, anoxic brain injury, traumatic brain injury, and others. Family members of brain-injured individuals correspond via the Internet into coalitions demanding that their loved ones receive hyperbaric oxygen therapy. There are anecdotal reports of benefit with hyperbaric oxygen following brain injury but there is little credible scientific evidence for efficacy of hyperbaric oxygen in brain injury. Clearly, what is needed to answer if hyperbaric oxygen improves brain injury are results from carefully designed multi-center, prospective, randomized controlled clinical trials. However, the implementation of such a Phase III clinical trial is challenging without information from Phase II trials. We propose to conduct a feasibility trial that may potentially guide a future Phase III clinical trial.