Auxin　is　an　important　phylohormone,　which　regulates　specific　physiological　responses　such　as　division,　elongation　and　differentiation　of　cells.　A　new　method　using　liquid　chromatography/electrospray　ionization　ion　trap　mass　spectrometry　(LC/ESI-ITMS)　has　been　developed　for　identification　and　quantitation　of　four　auxins.　Under　the　optimum　conditions,　four　auxins　(indole-3-acetic　acid,　indole-3-propionic　acid,　indole-3-butyric　acid　and　1-naphthyl　acetic　acid)　were　completely　separated　and　quantitated　within　7　min　with　a　minimum　detection　limit　of　8.0　ng　mL(-1)　with　relative　standard　deviations　lower　than　5.0%.　This　method　also　has　been　applied　to　analysis　of　auxins　in　Chinese　cabbage　where,　even　with　a　complicated　serious　background　perturbation　due　to　the　natural　biological　matrix,　the　mean　recoveries　ranged　from　77.5%　to　99.8%.　Finally,　we　discuss　the　MS-relevant　properties　of　the　identified　auxins　in　detail.　Copyright　(C)　2008　John　Wiley　&　Sons,　Ltd.