Enrofloxacin　(ENR)　and　its　metabolite　ciprofloxacin　(CIP)　were　determined　by　capillary　zone　electrophoresis　(CZE)　with　end-column　amperometric　detection.　The　effect　of　several　factors,　such　as　pH　and　concentration　of　running　buffer　solution,　separation　voltage,　injection　time,　and　working　potential,　on　CZE　were　investigated　to　establish　the　optimal　conditions　of　separation　and　detection.　Under　a　given　set　of　conditions　(pH　8.00　phosphate　buffer　solution　(20　mmol/L);　+0.95　V　for　the　working　potential;　18　kV　for　the　separation　voltage;　sample　injection　at　18　kV　for　10　s),　the　compounds　investigated　can　be　well　separated　and　detected　within　8　min.　Excellent　linearity　was　observed　between　peak　currents　and　concentration　of　analytes　in　the　range　from　0.034　to　70.0　mg/kg　for　these　two　compounds.　The　detection　limits　(S/N=　3)　for　enrofloxacin　and　ciprofloxacin　were　13.68　mg/kg　and　14.35　mg/kg,　respectively,　which　were　about　7-fold　lower　than　the　maximum　residue　limits　(MRLs)　established　by　the　European　Union.　A　simple　sample　pretreatment　method　was　developed　and　proved　to　be　effective　in　obtaining　good　recoveries　and　short　analysis　time.　The　developed　CE-AD　method　was　simpler,　faster,　and　less　cost　intensive　than　other　reported　methods,　and　allows　the　determination　of　ENR　and　its　metabolite　CIP　in　contaminated　eel　liver　samples　and　other　animal　tissue　samples　at　the　required　maximum　residue　limits.　©　2005　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.