Background:　The　objective　of　this　study　was　to　investigate　the　protective　effects　of　molecular　hydrogen,　a　novel　and　selective　antioxidant,　on　steroid-induced　osteonecrosis　(ON)　in　a　rabbit　model.　Methods:　Sixty　rabbits　were　randomly　divided　into　two　groups　(model　group　and　hydrogen　group).　Osteonecrosis　was　induced　according　to　an　established　protocol　of　steroid-induced　ON.　Rabbits　in　the　hydrogen　group　were　treated　with　intraperitoneal　injections　of　molecular　hydrogen　at　10　ml/kg　body　weight　for　seven　consecutive　days.　Plasma　levels　of　total　cholesterol,　triglycerides,　soluble　thrombomodulin(sTM),　glutathione(GSH)　and　malondialdehyde(MDA)　were　measured　before　and　after　steroid　administration.　The　presence　or　absence　of　ON　was　examined　histopathologically.　Oxidative　injury　and　vascular　injury　were　assessed　in　vivo　by　immunohistochemical　staining　of　8-hydoxy-2-deoxyguanosine(8-OHdG)　and　MDA,　and　ink　artery　infusion　angiography.　The　terminal　deoxynucleotidyl　transferase-mediated　dUTP　nick　end　labeling　(TUNEL)　assays　were　performed　to　measure　apoptosis.　Results:　The　incidence　of　steroid-induced　ON　was　significantly　lower　in　hydrogen　group　(28.6%)　than　that　in　model　group　(68.0%).　No　statistically　differences　were　observed　on　the　levels　of　total　cholesterol　and　triglycerides.　Oxidative　injury,　vascular　injury　and　apoptosis　were　attenuated　in　the　hydrogen　group　compared　with　those　in　the　model　group　in　vivo.　Conclusions:　These　results　suggested　that　molecular　hydrogen　prevents　steroid-induced　osteonecrosis　in　rabbits　by　suppressing　oxidative　injury,　vascular　injury　and　apoptosis.