Enantiomer　of　chiral　dipeptides　were　separated　by　CE-ESI-MS　in　a　bare　fused-silica　capillary　using　(1)-(18-crown-6)-2,3,11,12-tetracarboxylic　acid　(18C6H4)　as　the　chiral　selector.　As　18C6H　4　is　a　kind　of　nonvolatile　chiral　selector,　in　order　to　prevent　from　18C6H4　into　the　ion-source　of　CE-ESI-MS,　a　partial　filling　technique　was　employed　in　this　study.　Some　dipeptides　with　one　chiral　center　or　two　chiral　centers,　such　as　DL-Leu-DL-Leu,　D-Ala-D-Ala　and　L-Ala-L-Ala,　Gly-D-Phe　and　Gly-L-Phe　were　used　to　evaluate　this　CE-ESI-MS　system.　Optimized　conditions　were　achivevd　with　2.0　mol/L　acetic　acid　(pH　2.15)　as　the　running　electrolyte,　5mM　18C6H4　in　3.0　mol/L　acetic　acid　(pH　2.00)　was　injected　hydrodynamically　(50　mbar　for　960　s)　before　sample　injection.　In　total　7.5mM　acetic　acid　in　80%　v/v　methanol-water　was　used　as　the　sheath　liquid,　and　20　kV　applied　voltage　was　used.　Under　the　optimum　conditions,　these　dipeptides　were　separated　and　detected.　LODs　(defined　as　S/N　=　3)　of　this　method　were　0.20,　0.10,　0.05　and　0.10　mmol/L　for　D-Ala-D-Ala,　L-Ala-L-Ala,　DL-Leu-DL-Leu,　Gly-L-Phe　and　Gly-D-Phe,　respectively.　The　RSDs　(n　=　7)　of　the　method　were　0.68-2.08%　for　migration　times　and　2.32-5.24%　for　peak　areas.　The　proposed　method　was　also　successfully　applied　to　the　enantioselective　analysis　of　these　dipeptides　in　the　spiked　serum　samples　with　satisfactory　results.　©　2009　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA.