The concurrent effect of succinate administration to protect against oxygen toxicity and of hyperbaric oxygen (HBO) exposures to treat model gas gangrene in mice was tested to determine whether succinate would interfere with the therapeutic efficacy of HBO. HBO (seven 90-min exposures) at 3 atmospheres absolute pressure (ATA) had been shown to reduce significantly the mortality of mice injected with Clostridium perfringens suspended in 10 mug of Adrenalin. When succinate was tested with this system, mortality of HBO-exposed infected animals was again significantly reduced (79% control mortality versus 17% HBO-exposed mortality), indicating that succinate does not interfere with the action of HBO. Exposures to 4 ATA of O(2) were evaluated in the same model clostridial infection with succinate used to prevent oxygen toxicity. Five 30-min exposures at 4 ATA reduced the mortality of infected animals (62% control versus 6% HBO-exposed mortality). Intraperitoneal succinate injections (10 mmoles/kg) were given 20 to 25 min prior to four of the seven 3-ATA exposures and before three of the five 4-ATA exposures. The intermittent succinate injections gave significant protection against the development of oxygen toxicity in infected and noninfected mice at both O(2) pressures. These studies support the potential clinical use of succinate or other oxygen-protective agents (i) to shorten HBO exposure times by using higher pressures to deliver the necessary O(2) dose, (ii) to increase the O(2) dose for difficult clinical situations by using maximal exposures at 4 ATA or more prolonged exposures at 2 to 3 ATA, and (iii) to continue HBO exposures in patients who require treatment but develop symptoms of oxygen toxicity.