Polybrominated　diphenyl　ethers　(PBDEs)　had　been　used　extensively　in　electrical　and　electronic　products　as　brominated　flame　retardants.　PBDEs　are　widely　distributed　in　environment　media　and　wildlife　since　they　are　lipophilic　and　persistent,　resulting　in　bioaccumulation　and　bioamplification　through　food　chains.　Accumulation　of　PBDEs　in　the　environment　and　human　tissues　will　consequently　cause　potential　negative　effects　on　the　ecological　environment　and　human　health.　To　date,　some　in　vitro　and　in　vivo　studies　have　reported　that　PBDEs　possess　neurotoxicity,　hepatotoxicity,　immunotoxicity,　reproduction　toxicity,　endocrine　disrupting　activity　and　carcinogenicity.　BDE-47　is　one　of　the　most　predominant　PBDE　congeners　detected　in　human　tissues.　The　objective　of　this　study　is　to　investigate　whether　low　concentration　of　BDE-47　could　cause　hormesis　effect　in　the　human　hepatoma　HepG(2)　cells,　and　to　explore　the　possible　molecular　mechanism.　The　results　showed　that　low　concentration　of　BDE-47　(10(-10),　10(-9)　and　10(-8)M)　could　promote　cell　proliferation　and　cause　no　obvious　change　in　DNA　damage　or　cell　apoptosis,　while　the　high　concentration　significantly　inhibit　cell　proliferation.　Meanwhile,　the　reactive　oxygen　species　(ROS)　in　low　concentration　BDE-47　(10(-10),　10(-9)　and　10(-8)　M)　treated　groups　significantly　elevated　compared　with　the　control　group.　After　low　concentration　BDE-47　treatment,　the　expression　of　proliferating　cell　nuclear　antigen　(PCNA),　Cyclin　D1,　DNA-dependent　protein　kinase　catalytic　subunit　(DNA-PKcs)　and　phosphorylated　protein　kinase　B　(p-Akt)　in　the　HepG(2)　cells　was　markedly　up-regulated.　However,　in　DNA-PKcs　inhibited　cells,　the　promotion　effect　on　cell　proliferation　was　significantly　suppressed.　Cell　cycle　analysis　showed　a　significant　decrease　in　Cl　phase　after　exposure　to　low　concentration　of　BDE-47.　Moreover,　pre-exposure　to　low　concentration　BDE-47　seemed　alleviate　the　negative　effects　of　high　concentration　(50　mu　M)　exposure　to　cause　DNA　damage　and　apoptosis.　These　results　suggested　that　BDE-47　has　a　hormesis　effect　in　HepG(2)　cells　and　DNA-PKcs/Akt　pathway　may　be　involved　in　regulation　of　cell　proliferation　and　apoptosis.　(C)　2011　Elsevier　Ireland　Ltd.　All　rights