Compound-specific　carbon　isotope　ratio　analysis　is　a　promising　tool　to　assess　the　origins　and　fates　of　organic　contaminants　in　many　fields.　The　present　study　aims　to　investigate　the　isotope　effects　of　dichloro-diphenyl-trichloroethane　(DDT)　and　its　degradates　in　carrots　during　digestion　processes　simulating　the　human　gastrointestinal　tract.　To　accurately　interpret　isotopic　data　obtained　for　unreleased　DDTs　(p,p-DDT,　p,p-DDD　and　p,p-DDE)　from　carrots　during　digestion,　spiked　carrots　with　known　delta　C-13　values　of　DDTs　were　incubated　in　simulated　gastric　and　intestinal　solutions　using　a　static　in　vitro　model　of　the　human　gut.　The　delta　C-13　values　and　concentrations　of　DDTs　remaining　in　the　carrot　and　in　the　digestive　solutions　were　measured.　The　difference　in　the　delta　C-13　values　of　the　added　DDTs　and　the　matrix-bound　DDTs　after　digestion　was　always　＜0.50　parts　per　thousand,　which　is　within　the　technical　specification　of　the　analytical　system,　although　the　released　DDTs　increased　or　decreased　under　the　digestion　conditions.　The　study　demonstrated　that　there　were　no　significant　carbon　isotopic　fractionations　during　digestion.　To　our　knowledge,　this　is　the　first　report　demonstrating　the　isotope　effect　of　organic　compounds　during　stomach　and　small　intestine　digestion,　and　the　first　reported　isotope　analyses　of　DDTs.　Copyright　(C)　2008　John　Wiley　&　Sons,　Ltd.