X-ray　photoelectron　spectroscopy　(XPS)　is　harnessed　as　an　in　situ　efficient　characterization　technique　for　monitoring　chemical　bond　transformation　in　DNA　and　cisplatin-DNA　complexes　under　synergic　X-ray　irradiation.　By　analyzing　the　variation　of　relative　peak　area　of　core　elements　of　DNA　as　a　function　of　irradiation　time,　we　find　that　the　most　vulnerable　scission　sites　in　DNA　are　those　containing　phosphate　and　glycosidic　bonds.　Compared　to　DNA,　the　effective　rate　constants　of　the　corresponding　phosphodiester　and　glycosidic　bond　cleavages　for　cisplatin-DNA　complexes　are　1.8　and　1.9　folds　larger.　These　damages　and　their　enhancements　are　similar　to　those　induced　by　low　energy　electrons　(LEE).　Consistently,　the　magnitude　of　the　secondary　electron　distribution　produced　by　the　X-rays　on　the　cisplatin-DNA　complexes　is　considerably　increased　compared　to　that　of　pristine　DNA.　The　data　suggest　that　DNA　radiosensization　by　cisplatin　results　not　only　from　the　sensitization　of　DNA　to　the　action　of　LEE,　but　also　from　an　increase　the　production　of　LEE　at　the　site　of　binding　of　the　cisplatin.　The　results　provide　new　insights　into　the　mechanisms　of　cisplatin-induced　sensitization　of　DNA　under　X-ray　irradiation,　which　could　be　helpful　in　the　design　of　new　cisplatin-based　antitumor　drugs.　©　2013　American　Chemical　Society.