The basic mechanisms behind the pharmacologic effects of hyperbaric oxygen therapy are not clear. Reactive oxygen metabolites are generally associated with the adverse reactions to hyperbaric oxygen exposure but they are also believed to be involved in the antibacterial effects of this therapy. The possibility that reactive oxygen metabolites are responsible for some of the other reported beneficial effects of hyperbaric oxygen therapy has not been investigated. This hypothesis paper briefly reviews the literature suggesting that the pharmacologic actions underlying some of the beneficial effects of hyperbaric oxygen therapy may be caused by superoxide and/or hydrogen peroxide. Elucidation of the pharmacologic mechanisms is fundamental in order to fully exploit the therapeutic potential of hyperbaric oxygen and we incite experimental research to be done within this area.