Inflammation plays a key role in a variety of pain conditions including acute inflammatory injuries and more chronic conditions such as arthritis. Non-steroidal anti-inflammatory drugs provide effective relief for many patients with inflammatory pain, but long term use can be associated with deleterious side effects and a subset of patients receive limited relief. Hyperbaric oxygen therapy is an alternative therapy that has been used to treat a variety of ailments from carbon monoxide poisoning to fibromyalgia. Treatment involves administration of 100% oxygen at a pressure greater than atmospheric pressure at sea level. The purpose of this experiment was to explore the effect of hyperbaric oxygen treatment in both an animal model of acute inflammation and an animal model of arthritis. The acute inflammatory model involved .05 ml subcutaneous injection of 1% carrageenan in the left hind paw, and the arthritic model involved .12 ml intra-articular injection of 2% carrageenan in the left knee joint. Hyperbaric treatment involved exposing animals to 100% oxygen at pressure of 2.4 atmospheres for 90 minutes in hyperbaric chamber. A sham treatment group was placed in the chamber but did not receive treatment. To assess edema paw volume measures were used in the acute inflammatory model and joint diameter was used to in the arthritic model. Mechanical paw withdrawal thresholds were used to assess paw sensitivity in both models. Measures were taken prior to injection, previous to treatment, immediately following treatment and every hour up to 5 hours post-treatment. Hyperbaric oxygen treatment significantly decreased hypersensitivity following both subcutaneous and intra-articular carrageenan injection as compared to pre-treatment measure. In addition, treatment significantly decreased edema in the acute but not the arthritic model of inflammation as compared to pre-treatment measure. Clinically hyperbaric oxygen may be used in situations where NSAIDS are contraindicated or in chronic cases of inflammation.