Background　Hyperbaric　oxygen　preconditioning　(HBO)　is　a　new　method　of　ischemia　preconditioning.　In　this　study,　we　examined　its　effects　on　skin　flap　survival　and　the　mechanisms　involved.　Methods　Thirty-six　rats　were　divided　into　three　groups:　HBO　preconditioning,　control,　and　sham　groups.　An　extended　epigastric　adipocutaneous　flap　based　on　the　right　superficial　epigastric　artery　and　vein　was　raised.　A　3-hour　period　of　flap　ischemia　was　induced　by　clamping　the　pedicle　vessels　with　a　microvascular　clamp.　At　the　end　of　ischemia　induction,　the　clamp　was　removed　and　the　flap　was　resutured.　Rats　in　the　HBO　preconditioning　group　were　treated　with　HBO　four　times　before　surgery.　Microcirculation　in　the　skin　flap　was　measured　on　postoperative　days　1,　3　and　5.　The　size　of　the　flap　was　measured　on　postoperative　day　5,　before　the　animals　were　sacrificed.　Samples　of　the　skin　flap　were　prepared　and　stained　with　hematoxylin　and　eosin.　The　levels　of　tumor　necrosis　factor　(TNF)-alpha,　interleukin　(IL)-1　beta,　and　IL-6　in　the　flap　samples　were　measured.　Results　Surviving　flap　size　was　significantly　higher　in　the　HBO　preconditioning　group　compared　with　controls,　with　a　reduced　inflammatory　response　and　increased　perfusion.　IL-1,　TNF-alpha,　and　IL-6　levels　in　the　HBO　preconditioning　group　were　lower　than　in　controls.　Conclusions　HBO　preconditioning　improved　flap　survival　in　this　ischemia-reperfusion　rat　model.　The　mechanisms　responsible　for　this　effect　may　relate　to　attenuation　of　the　inflammatory　response　and　increased　flap　perfusion　following　HBO　preconditioning.