The　kinetics　and　mechanisms　of　hydroxyl　radical/hydrated　electron　reactions　with　dimethyl　phthalate　(DMP)　were　investigated　using　pulse　radiolysis　and　electron　beam　radiolysis　techniques.　The　bimolecular　rate　constants　for　the　reaction　of　hydroxyl　radical　and　hydrated　electron　with　DMP　were　measured　to　be　3.4　x　10(9)　M-1　s(-1)　and　1.6　x　10(10)　M-1　s(-1)　under　pulse　radiolysis　experiments,　respectively.　The　major　products　after　radiation　were　elucidated　by　LC/MS/MS　and　ion　chromatography　analysis.　It　was　found　that　DMP　degradation　had　different　mechanisms　in　oxidative　and　reductive　conditions:　hydroxyl　radical　attacked　aromatic　ring　of　DMP　leading　to　the　fracture　of　benzene　ring,　formed　a　series　of　byproducts　which　were　completely　mineralized　while　hydrated　electron　attacked　the　ester　group　of　DMP,　formed　the　product　of　phthalic　acid　in　reductive　conditions.　(C)　2010　Elsevier　Ltd.　All　rights　reserved.