Since there is evidence that the intracellular redox status is in a close correlation with the inflammatory microenvironment, and it can also be changed by HBO2, the aim of this study was to investigate the effects of HBO2 on the mRNA expression of HIF-1α, proinflammatory cytokines, and antioxidative enzymes in the gut and peripheral lymphoid organs of BALB/c mice with DSS-induced colitis. The gene discussed is HIF1A; the disease is colitis.